Following the outbreak of war between North Korea and South Korea on June 25, 1950, the United States mobilized a large contingent of troops to send into the beleaguered country. Initially, units occupying Japan were sent, but forces were eventually dispatched from the United States. In August 1950, Kouma, who was then a sergeant first class, sailed for Korea along with much of the 2nd Infantry Division. It arrived there in late August and was moved into the line at the Pusan Perimeter, where American troops were holding a tight defensive line around the port city of Pusan.