Explosion of the cruiser Tsukuba

On Sunday 14 January 1917, at about 3.15 p.m., a powerful explosion occurred in the forward magazine of the Japanese battlecruiser Tsukuba. The ship lay at anchor in the naval port of Yokosuka at the entrance to Tokyo Bay, near other large ships of the fleet. According to the Japanese press of the time, a column of brown smoke rose about a hundred metres, and sailors standing on deck were thrown into the water by the blast. The ship sank within some fifteen minutes. The harbour was shallow, so the masts, bridge and funnels remained above water. According to reports the force of the explosion broke windows in Kamakura, more than ten kilometres away.

Tsukuba was the first large warship designed and built entirely in Japan. She was ordered during the war with Russia, after the loss of two battleships to Russian mines. Built at the naval arsenal at Kure, she entered service in 1907 as an armoured cruiser with four 305 mm guns. Fast and heavily armed, she was in essence a forerunner of the battlecruisers, and in 1912 the Japanese reclassified her as one. In the autumn of 1914, after Japan entered the war, she joined the squadron of Vice-Admiral Yamaya Tanin, which searched the Pacific for Admiral von Spee’s German squadron and occupied the German islands north of the equator. Later she remained in Japanese waters, and in December 1915 she was the ship of Emperor Yoshihito during the great fleet review in Tokyo Bay.

That the casualties were not even heavier was owed to it being a Sunday. Half the crew had been given leave and were ashore. According to Japanese sources about 340 men remained on board. Boats from the ships in harbour, among them the battlecruisers Kongō, Haruna and Ikoma, the battleship Kawachi and the cruiser Tsugaru, immediately set off to the rescue. Figures for the number of dead vary. The navy bulletin of 15 January listed a few dead and more than 150 missing, while according to Japanese studies based on navy documents 125 men were killed and 27 went missing without trace. At a joint funeral on 21 January about 150 victims were mourned. Western studies, and following them the Polish and English Wikipedia, repeat a much higher figure of 305 killed.

As early as 16 January the navy appointed a board of inquiry under Rear-Admiral Katō Kanji, who three years earlier had himself commanded Tsukuba. In those years warships blew up from time to time through the spontaneous combustion of unstable propellant. That was how the British cruiser Natal was lost at the end of 1915, and in the autumn of 1916, at Sevastopol, the Russian battleship Imperatritsa Mariya. In Western literature the cause of Tsukuba’s explosion is also often linked to the decomposition of explosives. The Japanese board, however, ruled out spontaneous combustion and defects in the ship, and concluded that the fire had been started deliberately by a human hand. Suspicion fell on a missing sailor who was being questioned that day about a theft. He was said to have set the fire out of despair, but the truth was never established.

Japan lost one of her most powerful ships without a fight, at a time when her British ally was asking ever more urgently for naval assistance. The wreck proved too badly damaged to be worth rebuilding. Her armament and equipment were salvaged, and in September 1917 the ship was struck from the navy list.