佐賀の乱
In 1872, he entered the fledgling Imperial Japanese Army as a second lieutenant. He was soon promoted to lieutenant, and in February 1874, Ōdera participated in the suppression of the Saga Rebellion, followed by the Taiwan Expedition of 1874. He later served in the Hiroshima Military District, the IJA 12th Infantry Regiment, During the Satsuma Rebellion, he was a company commander. During the campaign, he lost his right ear to enemy gunfire, but was instrumental in taking Kumamoto Castle back from the rebels. Ōdera subsequently served with the IJA 11th Infantry Regiment, as a brigade commander in IJA 8th Infantry Regiment, and as a brigade commander in the Imperial Guards. He was promoted to captain in 1888, after which he served as chief of staff of the IJA 2nd Division, IJA 4th Division and IJA 1st Divisions. In February 1894 and he was sent to the United States and Europe as a military attaché, visiting France and Germany. He was planning to continue on to visit Russia when recalled to Japan over rising tensions with China.