A career army officer, Prince Sadanaru entered the military academy in 1873 and fought as a lieutenant in the Satsuma Rebellion.

Promoted to captain in 1878, he studied military tactics at the École Spéciale Militaire de Saint-Cyr in France and later in Germany in the 1870s.

Upon his return to Japan, he was promoted to major in 1881 and advocated the establishment of a Japanese version of an army General Staff based on the Prussian model.

In June, he was promoted to full general, and recalled to Japan to serve on the Supreme War Council, before being sent by Emperor Meiji on a diplomatic mission to the United States.

He was promoted to the largely ceremonial rank of field marshal in 1915, and awarded the Grand Collar of the Supreme Order of the Chrysanthemum in 1916.

The Prince died of influenza on February 5, 1923, at his vacation home in Cape Inubō and was accorded a state funeral.