In December 1949, Hamlett was ordered to the headquarters of General of the Army Douglas MacArthur as executive officer of the logistics section (G-4), GHQ, Japan. At the start of the Korean War, he served as chief of the Supply Division and later, as G-4 chief of planning, he supervised the logistics planning for the Inchon landing. In December 1951, he went to Korea himself as division artillery commander for the 24th Infantry Division.