When the Blenheim entered service in 1938, it was one of the fastest light bombers in the world. A versatile aircraft, the twin-engined Blenheim was easily produced and, early in the war served in large numbers both as a light bomber and long-range fighter. Blenheim losses during the fighting in France were as high as those of the Fairey Battle primarily because they flew in small formations without fighter escort. The fighter variant came about from a need for an aircraft to escort bombers on raids that were beyond the ranges of Spitfires and Hurricanes. A temporary measure, the Blenheim fighter was basically the bomber version with a quartet of guns grafted into the bomb bay and a reflector sight added for the pilot. Against enemy bombers it could and often did make kills but against fighters it was at a marked performance disadvantage and suffered high losses. Coastal Command found Blenheims good for convoy escort as German bombers which attacked Allied convoys were usually beyond the range of their own fighters allowing the Blenheims a fighting chance.
DEFENSIVE GUNS: The Blenheim has a top gun turret that protects against attacks from above, but is blocked to the rear by the airplane's tail. The turret initially mounted only a single .303 calibre Browning, but a second gun was added in mid-1940. A single gun (a second added in mid-1941) with a restriced field of fire protects the airplane's belly, but only to the rear.
