The Bolo was built by the Douglas Aircraft Company, based on its DC-2, and was developed to replace the Martin B-10. By 1940, it was considered to be underpowered, to have inadequate defensive armament, and to carry too small a bomb load. Many were destroyed during the attacks on Pearl Harbor and the Philippines in December 1941. In 1942, the surviving B-18s were relegated to antisubmarine, transport duty, and training. A B-18 was one of the first American aircraft to sink a German U-boat, U-654 on 22 August 1942 in the Caribbean. In 1934, the United States Army Air Corps put out a request for a bomber with double the bomb load and range of the Martin B-10, which was just entering service as the Army's standard bomber. In the evaluation at Wright Field the following year, Douglas showed its DB-1. It competed with the Boeing Model 299 (later developed into the Boeing B-17 Flying Fortress) and Martin 146. While the Boeing design was clearly superior, the crash of the B-17 prototype (caused by taking off with the controls still locked) removed it from consideration. During the depths of the Great Depression, the lower price of the DB-1 ($58,500 vs. $99,620 for the Model 299) also counted in its favor. The Douglas design was ordered into immediate production in January 1936 as the B-18. The DB-1 design was essentially that of the DC-2, with several modifications. The wingspan was 4.5 ft (1.4 m) greater. The fuselage was deeper, to better accommodate bombs and the six-member crew; the wings were fixed in the middle of the cross-section rather than to the bottom due to the deeper fuselage. Added armament included nose, dorsal, and ventral gun turrets. Preston Tucker's firm received a contract to supply a remote controlled gun turret for the aircraft. For information on the operational history and variants, click here. Specifications below are for the B-18A model.
