Born in what is now part of the city of Nantan, Kyoto prefecture, as the fourth son of a farmer, Ushiroku attended military preparatory schools in Osaka, and graduated from the 17th class of the Imperial Japanese Army Academy in 1905.

He served in combat very briefly at the very end of the Russo-Japanese War as a junior lieutenant with the IJA 38th Infantry Regiment.

In these roles, Ushiroku pushed for the use of suicide attacks by infantry to disable or destroy American armor due to Japan's inability to mass-produce effective anti-tank weapons by this stage of the war.

[5] After the collapse of the Tojo cabinet following the loss of Saipan, Ushiroku returned to Manchukuo to take command of the Japanese Third Area Army to oppose the Soviet invasion.

Although his forces were composed mostly of undertrained or overaged reservists with obsolete weapons, he refused orders to retreat, and launched a counterattack along the Mukden-Port Arthur railway, buying time to allow many Japanese civilians to flee.

By 13 August 1945, his formations were largely shattered, and a mutiny by the Manchukuo Imperial Army at Shinkyō ended his attempts to regroup.