The only son of the Confederate Civil War general of the same name, Buckner was commissioned in the infantry after graduating from the U.S. Military Academy at West Point, N.Y. (1908). Rising in rank, he became a brigadier general in the regular army and from August 1940 to June 1944 was commanding general, Alaska Defense Command, with headquarters at Fort Richardson, Alaska.

Following a short assignment to the central Pacific area, he was appointed (September 1944) commanding general of the 10th Army, holding the rank of lieutenant general. In that post he was charged with the invasion of the strategic Ryukyu Islands, which were still held tenaciously by the Japanese; he fought and won the Pacific front's last great land battle on Okinawa (April–June 1945). He was killed in action while visiting a forward observation post near the southwest tip of the island. The large naval anchorage on the east side of Okinawa, formerly called Nakagusuku Bay, was renamed Buckner Bay in his honour.