Under Ōba's leadership, the group survived for over a year after the battle and finally surrendered in December 1945, three months after the war had ended.

[3][4] In 1934, Ōba joined the 18th Infantry Regiment of the Imperial Japanese Army, based in the nearby city of Toyohashi.

[5] He was designated a Ground Officer Candidate, First Class, received specialized training, and was sent to Manchukuo, where the bulk of the 18th Regiment was already stationed on occupation duty.

[5][8] At about 3:00pm, 29 February, the transport ship carrying the regiment, the Sakito Maru, was struck by a torpedo fired by the American submarine USS Trout, near the island of Saipan.

[15] By 30 September 1944, the Japanese Army made an official presumption of death for all personnel of unknown status and they were declared killed in action.

When the soldiers were not assisting the civilians with survival tasks, Captain Ōba and his men continued their battle against the garrison of U.S. Marines.

Ōba used Mount Tapochau as their primary base; at 473 meters (1,552 ft), the peak offered an unobstructed 360-degree view of the island.

From their base camp on the western slope of the mountain, Ōba and his men occasionally conducted guerrilla-style raids on American positions.

[8] Due to the speed and stealth of these operations, and the frustrated attempts to find him, the Marines on Saipan eventually referred to Ōba as "The Fox".

[8][1] In September 1944, the Marines began conducting patrols in the island's interior, searching for survivors who were raiding their camp for supplies.

Although some of the soldiers wanted to fight, Captain Ōba asserted that their primary concerns were to protect the civilians and to stay alive to continue the war.

[19] Amō was then able to present documents from the defunct Imperial General Headquarters to Captain Ōba ordering him and his 46 remaining men to surrender themselves to the Americans.

Once back in Japan, Ōba was reunited with his wife and met his son for the first time; the child had been born in 1937, just after his father had left for China.

[4] Ōba was hired by the Maruei Department Store Company in 1952, where he was employed as a representative and spokesman for the board of directors until 1992.

[3][4] Hisamitsu showed the letters to his cousin, Keiichiro Hirano,[Notes 1] a novelist and the 1998 recipient of the prestigious Akutagawa Prize.

[3] They offered the task of publication to Mari Mizutani, of Toyohashi, who has stated that she believes the letters are especially significant for their detailed descriptions of daily life during the war; while both husband and wife wrote of their deep affection for each other, both also wrote about innumerable daily activities, Mineko in Gamagori and Ōba in China or on occupation duty in Manchuria, prior to being shipped to the Pacific.

On 11 February 2011, the film Taiheiyō no kiseki – fokksu to yobareta otoko (太平洋の奇跡−フォックスと呼ばれた男−, or, Miracle of the Pacific: The Man Called Fox (also titled "Oba: The Last Samurai")) was released in theaters,[23] portraying the struggles of Ōba and his group on Saipan, as well as the Marines' relentless manhunt.