After carrying out a series of command and staff assignments, he served in the United States and Europe during World War II in a number of senior positions. With the surrender of Japan imminent, Bonesteel, General George A. Lincoln, and Colonel Dean Rusk of the Strategy Policy Committee at the Pentagon were tasked with drawing up General Order No. 1 to define the areas of responsibility for American, Soviet and Chinese forces. On August 10, 1945, with Soviet forces already moving through Manchuria into northern Korea, Bonesteel proposed the 38th parallel as the Division of Korea. The draft General Order was cabled to the Soviets on 15 August and accepted by them the following day.[7]
In the postwar era, Bonesteel served as special assistant to the Secretary of State. In November 1958, in an official capacity, he visited Saigon, South Vietnam. He also served as commanding general of the 24th Infantry Division (1961–1962), and commanding general of the VII Corps (1962–1963).[8]