On July 19th, 1920, a battleship was laid down at the shipyard of Kawasaki Heavy Industries in Kobe, Japan. As part of the second Eight-Eight fleet composition plan (Eight battleships, eight armored cruisers/battlecruisers) and the ongoing naval arms race that had started before WWI, Japan was expanding its battlefleet with ever larger and more capable designs to maintain parity with the United States Navy in the Pacific.
This ship was the second of the Tosa class battleships. It would have run more than 39,000 tons of normal displacement, with five pairs of 16.1''/45 caliber guns, and a top speed of 26.5 knots. An upgrade over the previous Nagato class, but the plans for the Eight-Eight fleet would have seen even larger and more heavily armed ships over the next several years.
A model of what the Tosa class battleships would have looked like had they been completed.
The ship was launched on November 17th, 1921 and named 'Kaga' after the province which is now the Ishikawa Prefecture. Construction proceeded until February of 1922 when the Washington Naval Treaty went into effect. This treaty, signed by the United States, the United Kingdom, the Empire of Japan, the Kingdom of Italy, and the French Republic resulted in a 'battleship holiday' where no new ships were to be built for ten years, and construction on existing ships was to be halted.
Only by allowing the USN to retain USS West Virginia and the Royal Navy to construct a pair of 16''-armed battleships (the Nelson class) was the IJN allowed to retain the second Nagato class battleship, Mutsu. On July 22nd, 1922 the IJN took ownership of the partially completed hull and made plans to expend Kaga as a target. But events beyond the control of anyone were to intervene.
The Great Kanto Earthquake on September 1st, 1923 laid waste to a large area of the island of Honshu. Registering at 8.3 on the Richter Scale, more than 100,000 people were killed, both by the direct effects of the earthquake and in the ensuing fires, riots, and targeted crimes (including hundreds of ethnic Koreans and Chinese).
Another effect was at the Yokosuka Navy Yard, where the battlecruiser Amagi was undergoing conversion into an aircraft carrier under Article IX of the WNT. The ship was knocked off the ways and it was concluded that the stress damage to the hull made repairs impossible. So on November 19th, Kaga was ordered to be modified into an aircraft carrier to replace Amagi.
It would take until 1925 for the conversion to start as plans were drafted and the damage to Yokosuka was repaired, but on March 31st, 1928 Kaga was commissioned into the Japanese Navy.
Kaga anchored of Ikari, Japan, circa 1930.
Kaga, as converted, had a very different design to the wreck that has been found. Originally Kaga had three flight decks to allow for faster launching of aircraft, mounted 10 7.9'' guns, and an unconventional pipe-like funnel that directed all exhaust to the stern.
Kaga at Yokosuka Naval Arsenal, November 20th, 1928.
At this time her anticipated air wing consisted of a total of 60 aircraft. 12+4 Mitsubishi Type 10 1MF fighters, 24+4 Mitsubishi Type 13 B1M3 bombers, and 12+4 Mitsubishi Type 10 2MR reconnaissance planes. Though it wouldn't be until late 1929 that Kaga would actually embark aircraft.
Kaga underway in 1930, with B1M Type 13 and A1N Type 3 aircraft on her flight decks.
This configuration had an abundance of issues; the multiple decks limited the takeoff runs of heavier aircraft, the smoke from the funnels disrupted landing operations, and filled the non-commissioned officers quarters with exhaust.
Despite these shortcomings, Kaga saw service starting in 1932, after the 1931 "Mukden Incident". On September 18th, 1931 a Japanese force detonated a small cache of explosives near a railway line in Manchuria, then blamed it on nearby Chinese garrison. The next day the Japanese attacked in 'retaliation', resulting in the Japanese invasion and occupation of Manchuria.
Kaga's first combat mission began on January 29th, 1932 when she left the port of Sasebo as the flagship of Carrier Division One as part of the Third Fleet, bound for Shanghai.
Kaga on sea trials, September 15th, 1928.
After the Mukden Incident, anti-Japanese sentiment was high in China. On the 18th of January, a group of five Japanese Buddhist monks were assaulted by civilians in Shanghai, resulting in one of them being killed and two others seriously injured. Over the next several hours a factory was burned down, and a policeman who responded was killed. This resulted in even more anti-Japanese and anti-imperialist protesting in Shanghai, including street marches and boycotts.
Over the next several days the Japanese gathered 7,000 troops, 30 ships, and 40 aircraft in and around Shanghai, justifying the action that they needed to protect their citizens and concessions in the city. An ultimatum was issued that demanded official condemnation and financial compensation for the incident on the 18th, as well as efforts to minimize the public anti-Japanese sentiment. The municipal council agreed to these demands on the 28th of January. Despite this, the Japanese started to bomb the city, and by the time of the ceasefire on March 3rd, 10,000 to 20,000 Chinese civilians were dead. Chinese military forces had suffered heavy casualties and were not permitted to garrison troops in or near the city.
By October 1933 Kaga was moved to reserve status, being judged inferior to Akagi (the second ship of the Amagi class of battlecruisers) due to her lower speed, inferior flight deck system, and poor funnel. In June 1934 a massive reconstruction effort started to bring Kaga up to par with Akagi.
On June 25th, 1935 the work was finished. Kaga emerged from the shipyard with a single flight deck that ran the length of the ship (815' 6'' [248.55 meters]), extended hangers, and another elevator, allowing her to carry and operate up to 90 aircraft. New arresting gear was also added.
Kaga underway post refit with aircraft.
The turreted 7.9'' guns were removed, and newer 20cm guns were added in the stern casemates. Her original 12 cm AA guns were replaced with new 12.7cm/40 caliber Type 89 twin mounts, on raised sponsons that provided greater firing arcs. 11 of the decent for the time Type 96 twin 25mm mounts were mounted (one of which can be seen below), as were half a dozen 6.5mm Type 11 machine guns.
The long pipe funnel was replaced with a single downturned funnel on the starboard side (seen above). A small island was added forward of the funnel, also on the starboard side. While some consideration was given to adding a vertical funnel and larger island like western carriers such as the Lexington class, this was right at the time of the investigations into the Tomuzuru Incident, making the designers in the IJN very cautious about adding topweight to ships.
This island was very small. on the rear was an air control station a level above the flight deck, the bridge itself was only 15 feet above the level of the flight deck. Surrounded on three sides by windows, the 11x11 foot space had open entrances at the rear, and was totally unprotected.
Torpedo defense bulges were also added, increasing her beam from 97.1 feet (29.6 meters) to 106.6 feet (32.5 meters).
Before the work Kaga displaced 27,300 tons standard, and at the end Kaga tipped the scales at 38,200 tons.
In the summer of 1937, the Second Sino-Japanese War truly started with the Marco Polo Bridge Incident on July 7th. Kaga launched her first attack of the war on August 15th, and would operate off the coast of China extensively for the next several months.
Another major incident on the road towards a global war was on December 12th, when aircraft from Kaga attacked and sank the American riverboat Panay, killing three Americans and wounding 43 more crew and passengers.
USS Panay sinking.
The entire debacle is closed in 1938, with the official explanation being that it was an accidental attack, despite the large American flags painted on the top of the ship for identification from the air. Many at the time suspected that it was actually a deliberate attack, which might have been confirmed by messages that the US navy was able to decrypt.
In the end, the Japanese paid $2,214,007.36 as reparation money, and war didn't break out between the US and Japan.
Kaga post-modernization.
Over the course of October 1937 to December 1938, Kaga steamed more than 29,000 nautical miles, and her fighter fighters claimed a total of 17 Chinese aircraft shot down for the loss of five of their own.
The last significant refits that Kaga went through were in May and November 1940.
Kaga from the air in the late 1930s.
During these refits, an additional pair of vertical supports were added below the bow overhang of the flight deck as well as being further reinforced. Apparently, three compressed air catapults were added during the May refit, but these weren't very effective and were quickly removed, but sources are conflicting about the exact nature of these installations.
The hangers were expanded to allow for larger aircraft to be carried, the arresting gear was replaced with a more modern system, the bridge was upgraded, and another four twin 25mm mounts were added.
In November 1941, Kaga departed the home islands in the company of five other fleet carriers for the attack of Pearl Harbor. The extent of the attack is well known, and highly involved, so it will not be covered in detail here.
Over the rest of 1941 and into 1942, Kaga participated in the rapid expansion of the Japanese empire through the South Pacific, supporting several landing operations. On May 27th, she departed Hashirajima in the company of Akagi, Hiryu, and Soryu, bound for the American owned atoll of Midway. The objective was to secure the island as a base for aircraft and submarines and to hopefully draw the surviving American surface forces into a battle where they could be pinned in place and destroyed.
Kaga's air group went through several different types of aircraft as technology developed, with her final group at Midway consisting of 18 A6M2 'Zero' fighters, 18+2 D3A1 'Val' dive bombers, 27 B5N2 'Kate' torpedo/level bombers, and nine additional Zeros from the 6th Air Group to station on Midway once the atoll was invaded.
A fuller study of the development of Japanese carrier aircraft will be for another time, as the IJN rapidly improved and replaced aircraft based on their experiences in China against several different models of western fighters.
Despite what they expected, the Japanese did not act in secrecy and a force of three American aircraft carriers and Midway's own defenders were ready for the attack. Despite the catastrophic losses suffered by American torpedo bombers from the carriers, their sacrifice diverted attention away from the other threats high above the sea.
Kaga suffered several hits from American dive bombers on the morning of June 4th, 1942. The crews in the hanger decks were in the process of rearming her strike aircraft with torpedoes and armor-piercing bombs for attacks against warships, as well as refueling the aircraft from the earlier strike on Midway.
To launch another round of CAP fighters, Kaga had started a turn to port slightly before the attack started, which was tightened in an effort to evade the stream of dive bombers. Between 1020 and 1030, two squadrons of SBD Dauntless dive bombers from VB-6 and VS-6 (off USS Enterprise) made their dives on Kaga. Despite evading the first three bombs, and shooting down one of the planes, there were at least a dozen more bombers ready to deliver their payloads.
Earl Gallaher's bomb detonated in the crew spaces beside the upper hangar, setting several fires, and killing many exposed crewmen and the maintenance officer, Cdr. Yamazaki Torao.
Norman Kleiss's bomb nearly hit the forward elevator, jarring it loose before detonating in the fighter stowage area. By his own account, he was aiming directly for the red Hinomaru on the front of the flight deck.
The next bomb either landed directly ahead of, or right on top of, the island. Without any sort of real protection, the 500 pound bomb blasted the front of the island down to the steel supports and killed a large number of Kaga's senior officers, including her captain (Okada), her executive officer, (Capt. Kawaguchi Masaso), navigator (Cdr. Kodota Kazuharu), and her gunnery officer (LtCdr. Miyano Tosaburo). Hits three and four on the diagram are conflicting since the damage and casualties made keeping an accurate count of hits difficult.
Another bomb hit slightly to port amidships amid the confusion but by then the ship was doomed. Nearly every man in the upper hanger would have been wounded or killed outright in the first few seconds of the bombs hitting, and the spread of the bomb impacts was enough to ensure that damage control would be able to do little to save the ship.
In Japanese DamCon practice, parts of the hanger would be closed off with fireproof curtains and the fires would be dealt with locally. But with the multiple hits, which also destroyed both the port and starboard fire mains, local firefighting wasn't possible. The second bomb hit probably sent splinters into the generator for the emergency pumps, located on the portside 5'' gun sponson, rendering it useless.
Aside from the gutting of the damage control systems, there were tens of thousands of pounds of explosives scattered around the hangar. During the switch from land attack to anti-ship weapons, the heavy 800 kilogram (1,764.7 pound) bombs (of where there were an estimated 28) were stacked around an ordinance lift near the forward elevator. There were also around 40 250 kilogram (551 pound) bombs, and 20 1,800 pound torpedoes, each of which had 240 kilograms (529 pounds) of explosives in the warhead. Altogether, there was around 80,000 pounds of loose high explosives on Kaga's hangar decks when the American bombs hit.
The final nail in Kaga's coffin was that her avgas fuel lines had not been purged, and the aircraft in the hangers were being fueled for their attacks against the American fleet. Even if the fuel lines had been purged, there was at least 10,000 gallons of gas in the parked aircraft, more than enough for what came next.
Around 1035, the mix of fires and vaporizing avgas resulted in a massive explosion, so severe that the XO of the battleship Haruna was certain that it had killed everyone aboard Kaga. This explosion was followed by six successive blasts, but despite this Kaga limped along at two to three knots. The massive effort of her engineering crews to keep Kaga underway would cost two-thirds of them their lives as the inferno in the hangars closed off their only escape.
Over the next several hours, the fires weakened the structure, so that each successive explosion blew more parts of the hangar away from the ship. At nearly 1400, USS Nautilus fired a spread of four torpedoes at the halted ship, only one of which connected, and which failed to detonate.
By 1800, it was clear that Kaga was beyond saving despite having fairly solid watertight integrity. She had been burning for almost nine hours, and had several hundred pounds of high explosives reduce everything above the floor of the lower hangar deck to debris and scrap. Even if the fires were burning themselves out, the damage was done. There wasn't much of a chance that Kaga would ever sail again, even if she'd been towed back to Japan.
Artists depiction from Shattered Sword.
The American fleet was still somewhere to the east, and there was a possibility of a night surface action, for which the Japanese needed their destroyers with their deadly torpedoes. With no other acceptable option, Kaga, along with another of the Kido Butai's carriers, Soryu, were scuttled by destroyer torpedoes.
Around 1915 the destroyer Hagikaze fired two torpedoes at Kaga's starboard side from a few thousand yards away. The 1,000-pound warheads detonated just aft of Kaga's midships, and she slowly sank on an even keel by the stern. At 1925, Kaga slipped beneath the waves of the Pacific Ocean, taking 811 of her crew with her.
Some efforts were made to locate the wrecks of the ships lost at Midway. In 1998 Robert Ballard located and documented USS Yorktown. The next year the group Nauticos found some debris that was identified as being from Kaga, including a portion of a gun tub, but the bulk of the wreck remained elusive.
On October 17th, 2019 the R/V Petrel posted a video on Facebook announcing that Kaga had been found, including some video of the wreck.
Kaga came to rest about 17,700 feet (5,400 meters) below the surface, more than three and a quarter miles down. The damage is even more extensive than was reported by survivors, with what looks like most of the structure above the floor of the lower hanger scattered in the enormous debris field.
The Wreck
This mosaic of high-frequency sonar passes shows the extent of the damage, there is very little of the hangar and flight deck structure left attached to the rest of the hull. The video that was released goes from the starboard side of Kaga at the stern, forward to the bow, and then around and back towards the stern on the port side.
Kaga retained the casemate mounted 20 cm/50 (7.9") guns close to the stern; six of these were holdovers from when she was converted into a carrier, and four of them were added to replace the ones that were removed when the twin turreted mounts were removed in the mid-1930s.
Further along the starboard side is more damage, though exactly where and what is seen is hard to tell because of the extent of the damage.
A gun, probably one of Kaga's 12.7 cm/40 (5") Type 89s. She carried a total of sixteen of these weapons in eight twin mounts, four to each beam. Kaga carried the most of these weapons out of all of the carriers in the Kido Butai, Akagi didn't carry any Type 89s, and Hiryu and Soryu each had six twin mounts.
This especially heavy armament, combined with the sheer numbers of attackers is probably why Kaga was the only Japanese carrier to shoot down one of the dive bombers.
This shows what appears to be some sort of open hatch to a walkway, more of this walkway will be seen later, which will also show how deeply the wreck has sunk into the sediment.
In the background is what looks like part of a support for the upper hanger and the flight deck, but there wasn't any information on the exact location. There is a good chance that this is just forward of the hangar though since there look to be fixtures for attaching mooring lines on the deck.
The bundles of cables that can be seen in many places are degaussing cables, which used an electric current to reduce the magnetic field of the ship's hull. This was useful for minimizing the effects that the steel hull had on compasses, and it also helped protect ships from magnetically triggered weapons such as mines and torpedoes.
Here some of the anchor chains and chocks can be seen, in the slightly different angle below (taken from the R/V Petrel Instagram page) part of an anchor fluke can also be seen just poking through the mud.
This is part of the supports for the flight deck, probably right near the bow of the ship where the flight deck would overhang the hangar. Some more of this support structure can be seen in the two pictures below.
The prow of Kaga is buried fairly deep into the seabed, so there isn't any footage of the very end of the bow. I've seen an estimate that she might have been going as fast as 40 miles per hour on impact. In the video, there is archival audio from Norman Kleiss, where he recounts his attack on Kaga.
Around to the port side, this catwalk shoes how deeply the hull was driven into the seabed. According to the captions in the video, Kaga ended up about 44 feet (3.5 meters) into the silt and sand. The bulge on the upper right is probably the base for either a gun director or for a Type 89 gun mount, but since the diagrams of Kaga's port side are limited, and photographs seem to be non-existent, without a more expansive view of the area a definitive identification cannot be made.
Kaga's portside Type 89s were located in two groups, a single mount ahead of the island and a cluster of three farther astern, just slightly ahead of the casemate mounted 7.9'' guns. In the lower picture, the roller bearings for the mount can be seen.
Moving farther aft, following the catwalk.
This looks like part of the torpedo bulge that was added in the 1934-35 reconstruction. Whatever it is, it clearly suffered significant damage from the sinking.
The port side 7.9'' guns suffered serious damage, such as this one which is missing entirely from its barbette.
Each of these single mounts weighed 56.6 tons, and could elevate about from -5 to +25 degrees. At 25 degrees, an armor-piercing shell would travel about 25,000 yards
The 7.9'' had one inch (25.4 mm) of splinter armor, even when carried on heavy cruisers. On carriers, the probability of shellfire causing critical damage from hitting the casemates was probably not considered a serious risk, due to their small size relative to the hangers which would be filled with aircraft, fuel, and munitions.
The estimated rate of fire for these guns was 3 to 5 rounds per minute, and it's probable that each gun had 120 rounds allocated to it. These were bag charged guns, which means that loading involved loading a separate shell, ramming it into the breech, and then pushing bags of powder in behind it. An armor-piercing shell weighed 242.5 pounds, and the propellant charge (which was in two bags) weighed 71.76 pounds.
The last casemate is missing the barrel.
About 40-50 feet of the stern is missing, however, there isn't a good way to tell what exactly is seen here. Based on drawings this should be the boat deck, so the cylinder that can be seen might have been the base for a boat crane.
Sources:
General History
http://www.combinedfleet.com/kaga.htm - Tabular Record of Movement, General History.
http://www.combinedfleet.com/KAGA-Data-Page-Chen.htm - Data page, information on rebuilds and refits.
https://ww2db.com/photo.php?source=all&color=all&list=search&foreigntype=S&foreigntype_id=9 - Photographs of Kaga.
https://en.wikisource.org/wiki/Washington_Naval_Treaty,_1922 - Full text of the Washington Naval Treaty.
Warships of the Imperial Japanese Navy, 1869-1945. Hansgeorg Jentschura, Dieter Jung, Peter Mickel.
Shattered Sword: The Untold Story of the Battle of Midway. Johnathan Parshall, Anthony Tully.
Armament
http://www.navweaps.com/Weapons/WNJAP_79-50_3ns.php
http://www.navweaps.com/Weapons/WNJAP_5-40_t89.php
http://www.navweaps.com/Weapons/WNJAP_47-45_10ns.php
http://www.navweaps.com/Weapons/WNJAP_25mm-60_mg.php
Up to Date on 10/26/2019
May be updated as further information is released.
This ship was the second of the Tosa class battleships. It would have run more than 39,000 tons of normal displacement, with five pairs of 16.1''/45 caliber guns, and a top speed of 26.5 knots. An upgrade over the previous Nagato class, but the plans for the Eight-Eight fleet would have seen even larger and more heavily armed ships over the next several years.
The ship was launched on November 17th, 1921 and named 'Kaga' after the province which is now the Ishikawa Prefecture. Construction proceeded until February of 1922 when the Washington Naval Treaty went into effect. This treaty, signed by the United States, the United Kingdom, the Empire of Japan, the Kingdom of Italy, and the French Republic resulted in a 'battleship holiday' where no new ships were to be built for ten years, and construction on existing ships was to be halted.
Only by allowing the USN to retain USS West Virginia and the Royal Navy to construct a pair of 16''-armed battleships (the Nelson class) was the IJN allowed to retain the second Nagato class battleship, Mutsu. On July 22nd, 1922 the IJN took ownership of the partially completed hull and made plans to expend Kaga as a target. But events beyond the control of anyone were to intervene.
The Great Kanto Earthquake on September 1st, 1923 laid waste to a large area of the island of Honshu. Registering at 8.3 on the Richter Scale, more than 100,000 people were killed, both by the direct effects of the earthquake and in the ensuing fires, riots, and targeted crimes (including hundreds of ethnic Koreans and Chinese).
Another effect was at the Yokosuka Navy Yard, where the battlecruiser Amagi was undergoing conversion into an aircraft carrier under Article IX of the WNT. The ship was knocked off the ways and it was concluded that the stress damage to the hull made repairs impossible. So on November 19th, Kaga was ordered to be modified into an aircraft carrier to replace Amagi.
It would take until 1925 for the conversion to start as plans were drafted and the damage to Yokosuka was repaired, but on March 31st, 1928 Kaga was commissioned into the Japanese Navy.
Kaga, as converted, had a very different design to the wreck that has been found. Originally Kaga had three flight decks to allow for faster launching of aircraft, mounted 10 7.9'' guns, and an unconventional pipe-like funnel that directed all exhaust to the stern.
At this time her anticipated air wing consisted of a total of 60 aircraft. 12+4 Mitsubishi Type 10 1MF fighters, 24+4 Mitsubishi Type 13 B1M3 bombers, and 12+4 Mitsubishi Type 10 2MR reconnaissance planes. Though it wouldn't be until late 1929 that Kaga would actually embark aircraft.
This configuration had an abundance of issues; the multiple decks limited the takeoff runs of heavier aircraft, the smoke from the funnels disrupted landing operations, and filled the non-commissioned officers quarters with exhaust.
Despite these shortcomings, Kaga saw service starting in 1932, after the 1931 "Mukden Incident". On September 18th, 1931 a Japanese force detonated a small cache of explosives near a railway line in Manchuria, then blamed it on nearby Chinese garrison. The next day the Japanese attacked in 'retaliation', resulting in the Japanese invasion and occupation of Manchuria.
Kaga's first combat mission began on January 29th, 1932 when she left the port of Sasebo as the flagship of Carrier Division One as part of the Third Fleet, bound for Shanghai.
After the Mukden Incident, anti-Japanese sentiment was high in China. On the 18th of January, a group of five Japanese Buddhist monks were assaulted by civilians in Shanghai, resulting in one of them being killed and two others seriously injured. Over the next several hours a factory was burned down, and a policeman who responded was killed. This resulted in even more anti-Japanese and anti-imperialist protesting in Shanghai, including street marches and boycotts.
Over the next several days the Japanese gathered 7,000 troops, 30 ships, and 40 aircraft in and around Shanghai, justifying the action that they needed to protect their citizens and concessions in the city. An ultimatum was issued that demanded official condemnation and financial compensation for the incident on the 18th, as well as efforts to minimize the public anti-Japanese sentiment. The municipal council agreed to these demands on the 28th of January. Despite this, the Japanese started to bomb the city, and by the time of the ceasefire on March 3rd, 10,000 to 20,000 Chinese civilians were dead. Chinese military forces had suffered heavy casualties and were not permitted to garrison troops in or near the city.
By October 1933 Kaga was moved to reserve status, being judged inferior to Akagi (the second ship of the Amagi class of battlecruisers) due to her lower speed, inferior flight deck system, and poor funnel. In June 1934 a massive reconstruction effort started to bring Kaga up to par with Akagi.
On June 25th, 1935 the work was finished. Kaga emerged from the shipyard with a single flight deck that ran the length of the ship (815' 6'' [248.55 meters]), extended hangers, and another elevator, allowing her to carry and operate up to 90 aircraft. New arresting gear was also added.
The turreted 7.9'' guns were removed, and newer 20cm guns were added in the stern casemates. Her original 12 cm AA guns were replaced with new 12.7cm/40 caliber Type 89 twin mounts, on raised sponsons that provided greater firing arcs. 11 of the decent for the time Type 96 twin 25mm mounts were mounted (one of which can be seen below), as were half a dozen 6.5mm Type 11 machine guns.
The long pipe funnel was replaced with a single downturned funnel on the starboard side (seen above). A small island was added forward of the funnel, also on the starboard side. While some consideration was given to adding a vertical funnel and larger island like western carriers such as the Lexington class, this was right at the time of the investigations into the Tomuzuru Incident, making the designers in the IJN very cautious about adding topweight to ships.
This island was very small. on the rear was an air control station a level above the flight deck, the bridge itself was only 15 feet above the level of the flight deck. Surrounded on three sides by windows, the 11x11 foot space had open entrances at the rear, and was totally unprotected.
Torpedo defense bulges were also added, increasing her beam from 97.1 feet (29.6 meters) to 106.6 feet (32.5 meters).
Before the work Kaga displaced 27,300 tons standard, and at the end Kaga tipped the scales at 38,200 tons.
In the summer of 1937, the Second Sino-Japanese War truly started with the Marco Polo Bridge Incident on July 7th. Kaga launched her first attack of the war on August 15th, and would operate off the coast of China extensively for the next several months.
Another major incident on the road towards a global war was on December 12th, when aircraft from Kaga attacked and sank the American riverboat Panay, killing three Americans and wounding 43 more crew and passengers.
The entire debacle is closed in 1938, with the official explanation being that it was an accidental attack, despite the large American flags painted on the top of the ship for identification from the air. Many at the time suspected that it was actually a deliberate attack, which might have been confirmed by messages that the US navy was able to decrypt.
In the end, the Japanese paid $2,214,007.36 as reparation money, and war didn't break out between the US and Japan.
Over the course of October 1937 to December 1938, Kaga steamed more than 29,000 nautical miles, and her fighter fighters claimed a total of 17 Chinese aircraft shot down for the loss of five of their own.
The last significant refits that Kaga went through were in May and November 1940.
During these refits, an additional pair of vertical supports were added below the bow overhang of the flight deck as well as being further reinforced. Apparently, three compressed air catapults were added during the May refit, but these weren't very effective and were quickly removed, but sources are conflicting about the exact nature of these installations.
The hangers were expanded to allow for larger aircraft to be carried, the arresting gear was replaced with a more modern system, the bridge was upgraded, and another four twin 25mm mounts were added.
In November 1941, Kaga departed the home islands in the company of five other fleet carriers for the attack of Pearl Harbor. The extent of the attack is well known, and highly involved, so it will not be covered in detail here.
Over the rest of 1941 and into 1942, Kaga participated in the rapid expansion of the Japanese empire through the South Pacific, supporting several landing operations. On May 27th, she departed Hashirajima in the company of Akagi, Hiryu, and Soryu, bound for the American owned atoll of Midway. The objective was to secure the island as a base for aircraft and submarines and to hopefully draw the surviving American surface forces into a battle where they could be pinned in place and destroyed.
Kaga's air group went through several different types of aircraft as technology developed, with her final group at Midway consisting of 18 A6M2 'Zero' fighters, 18+2 D3A1 'Val' dive bombers, 27 B5N2 'Kate' torpedo/level bombers, and nine additional Zeros from the 6th Air Group to station on Midway once the atoll was invaded.
A fuller study of the development of Japanese carrier aircraft will be for another time, as the IJN rapidly improved and replaced aircraft based on their experiences in China against several different models of western fighters.
Despite what they expected, the Japanese did not act in secrecy and a force of three American aircraft carriers and Midway's own defenders were ready for the attack. Despite the catastrophic losses suffered by American torpedo bombers from the carriers, their sacrifice diverted attention away from the other threats high above the sea.
Kaga suffered several hits from American dive bombers on the morning of June 4th, 1942. The crews in the hanger decks were in the process of rearming her strike aircraft with torpedoes and armor-piercing bombs for attacks against warships, as well as refueling the aircraft from the earlier strike on Midway.
To launch another round of CAP fighters, Kaga had started a turn to port slightly before the attack started, which was tightened in an effort to evade the stream of dive bombers. Between 1020 and 1030, two squadrons of SBD Dauntless dive bombers from VB-6 and VS-6 (off USS Enterprise) made their dives on Kaga. Despite evading the first three bombs, and shooting down one of the planes, there were at least a dozen more bombers ready to deliver their payloads.
Earl Gallaher's bomb detonated in the crew spaces beside the upper hangar, setting several fires, and killing many exposed crewmen and the maintenance officer, Cdr. Yamazaki Torao.
Norman Kleiss's bomb nearly hit the forward elevator, jarring it loose before detonating in the fighter stowage area. By his own account, he was aiming directly for the red Hinomaru on the front of the flight deck.
The next bomb either landed directly ahead of, or right on top of, the island. Without any sort of real protection, the 500 pound bomb blasted the front of the island down to the steel supports and killed a large number of Kaga's senior officers, including her captain (Okada), her executive officer, (Capt. Kawaguchi Masaso), navigator (Cdr. Kodota Kazuharu), and her gunnery officer (LtCdr. Miyano Tosaburo). Hits three and four on the diagram are conflicting since the damage and casualties made keeping an accurate count of hits difficult.
Another bomb hit slightly to port amidships amid the confusion but by then the ship was doomed. Nearly every man in the upper hanger would have been wounded or killed outright in the first few seconds of the bombs hitting, and the spread of the bomb impacts was enough to ensure that damage control would be able to do little to save the ship.
In Japanese DamCon practice, parts of the hanger would be closed off with fireproof curtains and the fires would be dealt with locally. But with the multiple hits, which also destroyed both the port and starboard fire mains, local firefighting wasn't possible. The second bomb hit probably sent splinters into the generator for the emergency pumps, located on the portside 5'' gun sponson, rendering it useless.
Aside from the gutting of the damage control systems, there were tens of thousands of pounds of explosives scattered around the hangar. During the switch from land attack to anti-ship weapons, the heavy 800 kilogram (1,764.7 pound) bombs (of where there were an estimated 28) were stacked around an ordinance lift near the forward elevator. There were also around 40 250 kilogram (551 pound) bombs, and 20 1,800 pound torpedoes, each of which had 240 kilograms (529 pounds) of explosives in the warhead. Altogether, there was around 80,000 pounds of loose high explosives on Kaga's hangar decks when the American bombs hit.
The final nail in Kaga's coffin was that her avgas fuel lines had not been purged, and the aircraft in the hangers were being fueled for their attacks against the American fleet. Even if the fuel lines had been purged, there was at least 10,000 gallons of gas in the parked aircraft, more than enough for what came next.
Around 1035, the mix of fires and vaporizing avgas resulted in a massive explosion, so severe that the XO of the battleship Haruna was certain that it had killed everyone aboard Kaga. This explosion was followed by six successive blasts, but despite this Kaga limped along at two to three knots. The massive effort of her engineering crews to keep Kaga underway would cost two-thirds of them their lives as the inferno in the hangars closed off their only escape.
Over the next several hours, the fires weakened the structure, so that each successive explosion blew more parts of the hangar away from the ship. At nearly 1400, USS Nautilus fired a spread of four torpedoes at the halted ship, only one of which connected, and which failed to detonate.
By 1800, it was clear that Kaga was beyond saving despite having fairly solid watertight integrity. She had been burning for almost nine hours, and had several hundred pounds of high explosives reduce everything above the floor of the lower hangar deck to debris and scrap. Even if the fires were burning themselves out, the damage was done. There wasn't much of a chance that Kaga would ever sail again, even if she'd been towed back to Japan.
The American fleet was still somewhere to the east, and there was a possibility of a night surface action, for which the Japanese needed their destroyers with their deadly torpedoes. With no other acceptable option, Kaga, along with another of the Kido Butai's carriers, Soryu, were scuttled by destroyer torpedoes.
Around 1915 the destroyer Hagikaze fired two torpedoes at Kaga's starboard side from a few thousand yards away. The 1,000-pound warheads detonated just aft of Kaga's midships, and she slowly sank on an even keel by the stern. At 1925, Kaga slipped beneath the waves of the Pacific Ocean, taking 811 of her crew with her.
Some efforts were made to locate the wrecks of the ships lost at Midway. In 1998 Robert Ballard located and documented USS Yorktown. The next year the group Nauticos found some debris that was identified as being from Kaga, including a portion of a gun tub, but the bulk of the wreck remained elusive.
On October 17th, 2019 the R/V Petrel posted a video on Facebook announcing that Kaga had been found, including some video of the wreck.
Kaga came to rest about 17,700 feet (5,400 meters) below the surface, more than three and a quarter miles down. The damage is even more extensive than was reported by survivors, with what looks like most of the structure above the floor of the lower hanger scattered in the enormous debris field.
The Wreck
This mosaic of high-frequency sonar passes shows the extent of the damage, there is very little of the hangar and flight deck structure left attached to the rest of the hull. The video that was released goes from the starboard side of Kaga at the stern, forward to the bow, and then around and back towards the stern on the port side.
Kaga retained the casemate mounted 20 cm/50 (7.9") guns close to the stern; six of these were holdovers from when she was converted into a carrier, and four of them were added to replace the ones that were removed when the twin turreted mounts were removed in the mid-1930s.
From a caption in the video, this is another of the starboard side casemates, though apparently totally blown out. Based on the video, the sonar, and the cross-section from Shattered Sword below, it looks like everything above the lower hanger deck has been destroyed.
It is reasonable to assume that there won't be any aircraft identifiable in the debris field due to the intensity of the explosions and fires.
This is part of the uptakes to the funnel, one pair can be seen close to the camera on the left side, and another pair on the right side in the background. The exhaust of all twelve boilers was trunked into a single funnel, which was a source of considerable discomfort for Kaga's crew.
Further along the starboard side is more damage, though exactly where and what is seen is hard to tell because of the extent of the damage.
A gun, probably one of Kaga's 12.7 cm/40 (5") Type 89s. She carried a total of sixteen of these weapons in eight twin mounts, four to each beam. Kaga carried the most of these weapons out of all of the carriers in the Kido Butai, Akagi didn't carry any Type 89s, and Hiryu and Soryu each had six twin mounts.
This especially heavy armament, combined with the sheer numbers of attackers is probably why Kaga was the only Japanese carrier to shoot down one of the dive bombers.
This shows what appears to be some sort of open hatch to a walkway, more of this walkway will be seen later, which will also show how deeply the wreck has sunk into the sediment.
In the background is what looks like part of a support for the upper hanger and the flight deck, but there wasn't any information on the exact location. There is a good chance that this is just forward of the hangar though since there look to be fixtures for attaching mooring lines on the deck.
The bundles of cables that can be seen in many places are degaussing cables, which used an electric current to reduce the magnetic field of the ship's hull. This was useful for minimizing the effects that the steel hull had on compasses, and it also helped protect ships from magnetically triggered weapons such as mines and torpedoes.
Here some of the anchor chains and chocks can be seen, in the slightly different angle below (taken from the R/V Petrel Instagram page) part of an anchor fluke can also be seen just poking through the mud.
This is part of the supports for the flight deck, probably right near the bow of the ship where the flight deck would overhang the hangar. Some more of this support structure can be seen in the two pictures below.
The prow of Kaga is buried fairly deep into the seabed, so there isn't any footage of the very end of the bow. I've seen an estimate that she might have been going as fast as 40 miles per hour on impact. In the video, there is archival audio from Norman Kleiss, where he recounts his attack on Kaga.
Around to the port side, this catwalk shoes how deeply the hull was driven into the seabed. According to the captions in the video, Kaga ended up about 44 feet (3.5 meters) into the silt and sand. The bulge on the upper right is probably the base for either a gun director or for a Type 89 gun mount, but since the diagrams of Kaga's port side are limited, and photographs seem to be non-existent, without a more expansive view of the area a definitive identification cannot be made.
Kaga's portside Type 89s were located in two groups, a single mount ahead of the island and a cluster of three farther astern, just slightly ahead of the casemate mounted 7.9'' guns. In the lower picture, the roller bearings for the mount can be seen.
Moving farther aft, following the catwalk.
This looks like part of the torpedo bulge that was added in the 1934-35 reconstruction. Whatever it is, it clearly suffered significant damage from the sinking.
The port side 7.9'' guns suffered serious damage, such as this one which is missing entirely from its barbette.
Each of these single mounts weighed 56.6 tons, and could elevate about from -5 to +25 degrees. At 25 degrees, an armor-piercing shell would travel about 25,000 yards
The 7.9'' had one inch (25.4 mm) of splinter armor, even when carried on heavy cruisers. On carriers, the probability of shellfire causing critical damage from hitting the casemates was probably not considered a serious risk, due to their small size relative to the hangers which would be filled with aircraft, fuel, and munitions.
The estimated rate of fire for these guns was 3 to 5 rounds per minute, and it's probable that each gun had 120 rounds allocated to it. These were bag charged guns, which means that loading involved loading a separate shell, ramming it into the breech, and then pushing bags of powder in behind it. An armor-piercing shell weighed 242.5 pounds, and the propellant charge (which was in two bags) weighed 71.76 pounds.
The last casemate is missing the barrel.
About 40-50 feet of the stern is missing, however, there isn't a good way to tell what exactly is seen here. Based on drawings this should be the boat deck, so the cylinder that can be seen might have been the base for a boat crane.
Sources:
General History
http://www.combinedfleet.com/kaga.htm - Tabular Record of Movement, General History.
http://www.combinedfleet.com/KAGA-Data-Page-Chen.htm - Data page, information on rebuilds and refits.
https://ww2db.com/photo.php?source=all&color=all&list=search&foreigntype=S&foreigntype_id=9 - Photographs of Kaga.
https://en.wikisource.org/wiki/Washington_Naval_Treaty,_1922 - Full text of the Washington Naval Treaty.
Warships of the Imperial Japanese Navy, 1869-1945. Hansgeorg Jentschura, Dieter Jung, Peter Mickel.
Shattered Sword: The Untold Story of the Battle of Midway. Johnathan Parshall, Anthony Tully.
Armament
http://www.navweaps.com/Weapons/WNJAP_79-50_3ns.php
http://www.navweaps.com/Weapons/WNJAP_5-40_t89.php
http://www.navweaps.com/Weapons/WNJAP_47-45_10ns.php
http://www.navweaps.com/Weapons/WNJAP_25mm-60_mg.php
Up to Date on 10/26/2019
May be updated as further information is released.
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