He graduated from the 25th class of the Imperial Japanese Army Academy in 1913, and served in the Siberian Intervention from April 1918 to December 1920.

On May 29, the last of the Japanese forces suddenly attacked near Chichagof Harbor in the first and only instance of a banzai charge on American soil.

The charge was led by Yamasaki himself, who was killed later that day, sword in hand and assaulting Engineer Hill.

After furious, brutal, close-quarter, and often hand-to-hand combat, the entire Japanese force was killed almost to the last man: only 29 prisoners were taken, with none of them officers.

American burial teams counted 2,351 Japanese dead, but it was presumed that hundreds more had been buried by bombardments over the course of the battle.