Before hostilities began, it had been agreed between the United Kingdom and France that in case of war, the short-range aircraft of Bomber Command would move to French airfields to operate against targets in Nazi Germany. Using the bombers for attacks on strategic targets in Germany was set aside, due to Anglo-French reluctance to provoke German retaliation; attacks on German military forces and their communications were substituted. The Battle squadrons suffered 40 per cent losses on 10 May, per cent on 11 May and 63 per cent on 12 May.
In 48 hours the number of operational AASF bombers fell from to More than half the bombers were lost, bringing AASF losses to 75 per cent. The remaining bombers began to operate at night and periodically by day, sometimes with fighter escorts. Experience, better tactics and periods of bad weather from 15 May to 5 June led to losses of 0. Once British rearmament began, the air policy of the British government was to have air defences sufficient to defeat an attack and an offensive force equal to that of the Luftwaffe.
With no land border to defend, British resources had been concentrated on radar stations, anti-aircraft guns and increasing the number of the most modern fighter aircraft. If Germany attacked, the British intended to take the war to the Germans by attacking strategically important targets with its heavy bombers, types unsuitable for operations in direct support of land forces.
In the RAF expansion programme was intended to provide means for the air defence of Britain and for counter-offensive operations against Germany. Army co-operation received few resources and no plans were made for RAF participation in mass land operations or the dispatch abroad of large expeditionary air forces. The Western Plan was devised by the Air Ministry for mobilisation and the deployment of squadrons to their wartime airfields.
Provision was made for the immediate dispatch of an Advanced Air Striking Force of ten squadrons to France, followed by a second echelon of ten more.
