This is the story of an event in Japanese naval history concerning the heroic death of Lieutenant Sakuma and his crew in Submarine No. 6 of the Imperial Japanese Navy.

Submarine No. 6 (Holland Type) was the nation’s first-built submarine, the smallest of its type. It left Kure Port for a training mission on April 11th in 1910. In those days submarine trainings were dangerous using less advanced equipment and techniques. Four days after their departure, while engaged in a practice dive in the Inland Sea, mechanical errors occurred. Seawater started flowing into the boat through the ventilator. When the crew attempted to close the sluice the chain broke.

Electricity was cut off, the gauge was invisible, wires were burned, and poisonous gas prevailed. The crew tried to pump the water out by hand but eventually the small submarine went off balance and sank at 10 A.M, 15th of April off Shinminato near Iwakuni.

Two days later the submarine was discovered at a depth of 16m. Unlike former submarine accidents, each crewmember of No.6 was found dead at their posts fulfilling their duties. Near the hatch, there was no sign of rushing to escape as was seen in former accidents. Lieutenant Sakuma told his men to behave calmly and they followed their commander to the last minute of death. As the submarine was sinking, Sakuma managed to write a Will in the wet and cold with the help of dim light coming through a small window of the conning tower. It was found in his locker and addressed to the Navy Department as a confidential report.

Sakuma began his Will:

“I must apologize for my failure that sank His Majesty’s submarine and killed subordinates. However, I am certain with pride that every crewmember operated with utmost coolness and never gave up their duties until their last hours....”

He also asked authorities not to let the disaster affect future development of submarines. He earnestly hoped that His Majesty would supply a means of living to the poor families of the crew. At the end of his Will Sakuma sent his best regards to his superiors mentioning each of them by name. On 20th of April, a national funeral was held at Kure Naval Station.

This incident spread throughout the world and Sakuma was admired for his courage and steadfastness. His story had once been written about in Japanese school text books. There are displays of his salvaged diary, with its English translation, in the Capitol, USA and the Royal Navy Submarine Museum Archive in Gosport, England.

In November 1912, a monument was unveiled on the grounds of Tainomiya Shrine, at Nishimitsuta, Kure. It is 19 m high and stands on the hill above the city where in the past Kure Bay could be seen without tall buildings. Since then a memorial ceremony has been held annually by the Association of Lighting Submarine No.6 Martyrdom. The screw and chain of the submarine rest at the foot of the monument.

Marking the 100th year of martyrdom, a memorial service took place at 10:30 A.M. on April 15th at Tainomiya Shrine. It was attended by 650 people.

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A True Hero

Tsutomu Sakuma (佐久間 勉) was 31 years old when he died an honorable death. Sakuma was born in Fukui prefecture in 1879, the second son of a Shinto priest. He was an excellent student and won scholarships. He studied at Japanese Naval Academy in Etajima. As a naval officer he served during the Russo-Japanese War. Sakuma married Tsugiko in Kyoto in 1908, but the next year unfortunately, Tsugiko passed away after giving birth to their daughter.

The memorial service was attended by Sakuma’s grandson.