Operation Raid on Yokosuka

The 'Raid on Yokosuka' was an air raid by carrierborne aircraft of Admiral William F. Halsey’s US 3rd Fleet against Japanese naval forces in the closing stages of World War II (18 July 1945).

The Japanese battleship Nagato was the raid’s primary target, although anti-aircraft positions and other warships at the Yokosuka naval arsenal were also attacked. Other US Navy and Royal Navy aircraft struck airfields in the Tokyo area.

While Nagato was only lightly damaged, the US aircraft sank one destroyer, one submarine and two escort vessels, and also damaged five small vessels. The Allied pilots also claimed the destruction of several locomotives and 43 Japanese aircraft as well as damage to another 77 aircraft. Japanese anti-aircraft guns shot down 12 US and two British aircraft.

During July 1945 the US 3rd Fleet, which was commanded by Halsey, conducted a series of air raids and naval bombardments against targets in Japan. These attacks were made by the 3rd Fleet’s fast carrier striking force, Task Force 38 commanded by Vice Admiral John S. McCain and comprising nine fleet carriers, six light carriers and their escorts. Almost 1,000 aircraft were embarked on the carriers. On 10 July TF 38’s aircraft struck airfields around Tokyo and claimed to have destroyed 340 Japanese aircraft on the ground and two in the air. No Japanese aircraft responded to this attack as they were being held in reserve to mount large-scale suicide attacks on the Allied fleet during the expected invasion of the country later in 1945. After this raid, the 3rd Fleet undertook raids on Hokkaido and the northern part of Honshu on 14 and 15 July, sinking large numbers of ships and destroying 25 aircraft on the ground. The US ships then sailed to the south and on 16 July were joined by Admiral Sir Bruce Fraser’s British Pacific Fleet’s main striking force, which was designated Task Force 37 and comprised three fleet carriers and their escorts under the command of Vice Admiral Sir Bernard Rawlings.

By July 1945 the Imperial Japanese navy’s remaining major warships were not longer able to put to sea for lack of adequate bunker oil and the overwhelming threat posed by Allied warplanes and submarines. While most of these Japanese warships were anchored near the major naval base at Kure and other locations in the Inland Sea, Nagato and several smaller warships were stationed at the Yokosuka naval arsenal in Tokyo Bay. At this time the battleship was moored alongside a pier facing to the north-west and covered in camouflage intended to make her difficult for aircraft to spot. All of Nagato's secondary armament and about half her anti-aircraft armament had been removed and emplaced on nearby hills from where they could provide protection to the naval base. Although the battleship’s boilers were not lit, she received steam and power from the submarine chaser Fukugawa Maru No. 7 and an auxiliary boiler located on the pier. The destroyer Ushio was also docked nearby in a position from which she was able to protect the battleship with her 25-mm anti-aircraft guns.

Nagato's presence at Yokosuka was revealed to the Allies by photographs taken during the 10 July raid on the Tokyo area. On 16 July Halsey and Rawlings met to plan raids on the Tokyo area. Halsey was determined to sink the remnants of the Imperial Japanese navy, and placed a particularly strong emphasis on attacking Nagato as she had been Admiral Isoroku Yamamoto’s flagship in the period of the 'Ai' attack on Pearl Harbor in December 1941. As the battleship was well positioned within a well defended harbour, the 3rd Fleet’s planners assessed that aircraft which attempted the straight and level flight needed to launch torpedoes against her would suffer heavy losses, and so decided instead to employ dive-bombing tactics. As the landward side of the naval base was mountainous, the approaches which could be used by dive-bombers were limited.

On 17 July the fleet of US and British warships attempted to strike the Yokosuka naval arsenal and other targets in the Tokyo area. Two waves of aircraft were despatched, but the attack was frustrated by heavy cloud over the target area and further attacks were cancelled. The aircraft which reached the Tokyo area struck airfields to the north of the Japanese capital but caused little damage. While the naval base was not attacked, it was overflown by a US fighter and its defenders were readied to respond to attacks. On the night of 17/18 July US and British warships bombarded the city of Hitachi.

On the following day, the Allied fleet sailed to the south looking for weather which was better suited or the conduct of flight operations. Conditions improved during the morning, and at 11.30 the day’s air strikes began to take-off. The British aircraft of TF 37 were despatched against airfields in the Tokyo area. The size of this attack was considerably reduced from what had been schemed, however, as the fuel system on board Victorious had become contaminated with water and the carrier could launch only six Vought F4U Corsair single-engined fighter-bombers. TF 38’s main effort was directed against the Yokosuka naval arsenal, Nagato again being designated the raid’s primary target. A smaller number of US aircraft was also despatched to attack Japanese airfields.

The attack on Yokosuka began at about 15.30 on 18 July. The first wave of US aircraft attacked the anti-aircraft batteries around the naval base, and succeeded in neutralising them. Following this, the aircraft of the VF-88 fighter squadron attacked Nagato with bombs. A 500-lb (227-kg) general-purpose bomb struck the battleship’s bridge, killing her commanding officer, Rear Admiral Otsuka Miki, as well as the executive officer and at least nine other men. Another 500-lb (227-kg) bomb later struck Nagato and detonated near her officer’s mess, killing about 22 sailors and knocking out four 25-mm guns. The only other direct hit on the ship was made by a 5-in (127-mm) shell or rocket which did not explode. In addition, 60 bombs landed in the harbour near Nagato, causing breaches to her double hull through which 2,000 tons of water flooded into the ship. By the time the attack came to an end at 16.10, 35 of the battleship’s 967 officers and men had been killed. The overall damage to the ship was later assessed as light.

US aircraft also attacked several other ships docked at Yokosuka. The incomplete 'Matsu' class destroyer Yaezakura broke in two and sank after being bombed, and the submarine I-372 was destroyed by another bomb; at the time the submarine’s crew was ashore and did not suffer any fatalities. Two escort vessels and a torpedo boat were also sunk. In addition to these losses, five other ships, including the obsolete destroyer Yakaze and the training ships Fuji and Kasuga, were damaged. Despite their proximity to Nagato, Fukugawa Maru No. 7 and Ushio were not damaged. The British and US aircraft despatched against airfields claimed to have destroyed 43 Japanese aircraft and damaged another 77. The pilots of these aircraft also claimed the destruction of several railway locomotives. The Allied losses in the attacks were 12 US Navy aircraft, two Royal Navy aircraft and 18 aircrew.

Following its attacks on the Tokyo Bay area on 18 July, the Allied fleet steamed away from Japan for refuelling. Its next attacks were made against the main body of the Imperial Japanese navy in Kure and the Inland Sea on 24, 25 and 28 July. These raids sank three battleships, one aircraft carrier and several other warships, but cost the Allies 133 aircraft destroyed and 102 aircrew killed. The 3rd Fleet and elements of the British Pacific Fleet continued attacks on targets in Japan until the end of the war on 15 August 1945.

After the attack on Yokosuka, the Nagato's crew removed all casualties from the ship and conducted limited repairs. Some of the ship’s ballast tanks were also flooded to give the impression that she had been sunk. During the early hours of 2 August, Nagato was ordered to put to sea to intercept an Allied naval force, but the sortie was cancelled before she had completed preparations to leave port as the report of Allied ships was found to be false.

At the time of Japan’s surrender on 15 August 1945, Nagato was the only Imperial Japanese navy battleship still afloat. On 30 August the ship was surrendered to the US Navy, and later became one of the target ships for the two atomic bomb tests conducted at Bikini atoll on 1 and 28 July 1946 during the 'Crossroads' operation, and sank during the night of 29/30 July.