During the Battle of Britain, which began in earnest on August 8,1940, Hurricanes concentrated mainly on the destruction of the German Heinkel He 111 and Dornier Do 17 bombers. These were the aircraft that would cause the most damage if allowed to get through. When it became clear that the Hurricane was becoming outclassed as a pure fighter, other duties were assigned to it. In October 1941 the 'Hurribomber' fighter-bomber came into being, carrying either two 113 kg (250 lb) or two 226 kg (500 lb) bombs under its wings. The Mk IID of 1942 was fitted with two 40 mm cannon for tank busting and two machine-guns, and was operated mainly in North Africa against Rommel's desert forces and in Burma against the Japanese. Other Hurricanes carried rocket projectiles as alternative ground attack weapons.