The Douglas SBD Dauntless was one of the truly great aircraft of World War II. It played a major role throughout the Pacific. On June 4, 1942, during the Battle of Midway, SBDs destroyed four Japanese carriers, dramatically altering the course of the war. The SBD's design was based on the Northrop BT-1, but with engine and structural changes. Production orders were placed in April 1939, with all SBD-1s going to U.S. Marine Corps units.