The RAF underwent rapid expansion prior to and during the World War II. Under the British Commonwealth Air Training Plan of December 1939, the air forces of British Commonwealth countries trained and formed “Article XV squadrons” for service with RAF formations.Under a parallel agreement, the Joint Air Training Scheme, South Africa trained 33,347 aircrew for the South African Air Force , the Royal New Zealand Air Force and other Allied air forces. This number was exceeded only by Canada, which trained 131,500 personnel. Many individual personnel from these countries, and exiles from occupied Europe, also served with RAF squadrons. By the end of the war the Royal Canadian Air Force had contributed more than 30 squadrons to serve in RAF formations, similarly, approximately a quarter of Bomber Command’s personnel were Canadian. Additionally, the Royal Australian Air Force represented around nine percent of all RAF personnel who served in the European and Mediterranean theatres.
In the Battle of Britain in 1940, the RAF (supplemented by 2 Fleet Air Arm Squadrons, Polish , Czecho-Slovak and other multinational pilots and ground personnel) defended the skies over Britain against the numerically superior German Lufwaffe . In what is perhaps the most prolonged and complicated air campaign in history, the Battle of Britain contributed significantly to the delay and subsequent indefinite postponement of Adolf Hitler’s plans for an invasion of the United Kingdom (Operation Sealion) . In the House of Commons on 20 August, prompted by the ongoing efforts of the RAF, Prime Minister Winston Churchill eloquently made a speech to the nation, where he said “Never in the field of human conflict was so much owed by so many to so few.
The largest RAF effort during the war was the strategic bombing campaign against Germany by Bomber Command . While RAF bombing of Germany began almost immediately upon the outbreak of war, under the leadership of Air Chief Marshal Bomber Harris, these attacks became increasingly devastating from 1942 onward as new technology and greater numbers of superior aircraft became available. The RAF adopted night-time area bombing on German cities such as Hamburg and Dresden, and developed precision bombing techniques for specific operations, such as the “Dambusters” raid by No 617 Squadron with Wing Commander Guy Gibson, or the Amiens prison raid known as Operation Jericho.
Allied bombing of German cities killed between 305,000 and 600,000 civilians. One of the most controversial aspects of Bomber Command during World War II was the area bombing of cities. Until 1942 navigational technology did not allow for any more precise targeting than at best a district of a town or city by night bombing. All large German cities contained important industrial districts and so were considered legitimate targets by the Allies. New methods were introduced to create “firestorms”. The most destructive raids in terms of casualties were those on Hamburg (45,000 dead) in 1943 and Dresden (25,000–35,000 dead) in 1945. Each caused afirestorm and left tens of thousands dead. Other large raids on German cities which resulted in high civil casualties were Darmstadt (12,300 dead), Pfozheim (17,600 dead) and Kassel (10,000 dead).
A Bomber Command crew member had a worse chance of survival than an infantry officer in World War I; more people were killed serving in Bomber Command than in the Blitz, or the bombings of Hamburg or Dresden. By comparison, the US Eight Air Force , which flew daylight raids over Europe, had 350,000 aircrew during the war and suffered 26,000 killed and 23,000 POWs. Of the RAF Bomber Command personnel killed during the war, 72 percent were British, 18 percent were Canadian, 7 percent were Australian and 3 percent were New Zealanders.
In total 364,514 operational sorties were flown, 1,030,500 tons of bombs were dropped and 8,325 aircraft lost in action.