of Japan In June 1944, Boeing B-29 Superfortresses launched from China, bombed Japanese factories. From November 1944, increasingly intense raids were launched from bases closer to Japan. Tactics evolved from high-altitude to lower altitude attacks, largely removing most defensive guns and switching to incendiary bombs. These attacks devastated many Japanese cities. In August 1945, B-29 Superfortresses dropped atomic bombs on Hiroshima and Nagasaki while the Soviets invaded Manchuria. The Japanese then surrendered unconditionally, officially ending World War II. Tactical air support By contrast with the British strategists, the primary purpose of the Luftwaffe was to support the Army. This accounted for the presence of large numbers of medium bombers and dive bombers on strength and the scarcity of long-range heavy bombers. This 'flying artillery' greatly assisted in the successes of the German Army in the Battle of France (1940) . Hitler determined air superiority was essential for the invasion of Britain. When this was not achieved in the Battle of Britain, the invasion was canceled, making this the first major battle whose outcome was determined primarily in the air. The war in Russia forced the Luftwaffe to devote the majority of its resources to providing tactical air support for the beleaguered German army. In that role, the Luftwaffe used the Junkers Ju 87, Henschel Hs 123 and modified fighters such as Messerschmitt Bf 109s and Focke-Wulf Fw 190s. The Red Air Force was also primarily used in the tactical support role, and towards the end of the war was very effective in the support of the Red Army in its advance across Eastern Europe. An aircraft of major importance to the Soviets was the Ilyushin Il-2 Sturmovik "flying artillery" which made life very difficult for panzer crews, and the Il-2 played an important part in the Soviet victory in one of the biggest tank battles in history at Kursk. Military transport and use of airborne troops Military transport was invaluable to all sides in maintaining supply and communications of ground troops, and was used on many notable occasions such as resupply of German troops in and around Stalingrad after Operation Uranus, and employment of airborne troops. After the first trials in use of airborne troops by the Red Army displayed in the early 1930s many European nations and Japan also formed airborne troops, and these saw extensive service on in all theatres of the Second World War. However their effectiveness