The Douglas B-18 Bolo medium bomber served with the United States Army Air Corps and the Royal Canadian Air Force (as the Douglas Digby) during the late 1930s and early 1940s. 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 carried too small a bomb load.