The first series, Army Air Force Historical Office, contains material Watson collected while serving as the Chief of the Southwest Pacific Branch of the Army Air Force Historical Office. The work of the office was eventually collected in the seven volume series, The Army Air Forces in World War II, edited by Wesley Frank Craven and James Lea Cate. Watson's contributions to the series pertain chiefly to Vols. I and IV. Types of material in this series include general correspondence about the work of the Historical Office, newspaper clippings chronicling daily events, and notes taken from primary wartime documents on Southwest Pacific Air Operations. Major events include Rabaul, Battle of the Bismarck Sea, Philippines campaign, Pearl Harbor, Wau, and Nassau Bay. Strategic topics include bombing techniques, equipment, men and morale, radio and radar, supplies, and allocations. There are also draft chapters of his work, The Fifth Air Force in the Huon Peninsula Campaign. Also included are several reference works such as maps of the Southwest Pacific, a gazetteer of New Guinea, and several works by J.V. Cragg on the Fifth Air Force.