Following the inter-Allied Casablanca Conference in January 1943 the outline for the Combined Bomber Offensive was agreed and resulted in early February with the 'Casablanca Directive'. This required the "progressive destruction and dislocation of the German military, industrial and economic systems and the undermining of the morale of the German people to a point where their capacity for armed resistance is fatally weakened". This directive was clarified in June when the Combined Chiefs of Staff issued the Point-blank Directive that stated that the highest priority targets were the fighter aircraft factories to ensure that in the coming invasion of France the enemy would not have air superiority. When these directives were issued it was envisaged that as well as attacks by RAF Bomber Command and the US Eighth Air Force based in England, the strategic bomber forces in Italy would begin operations once suitable bases were available. After the Allied landings in Italy and resulting collapse of the Italian fascist regime a network of bomber bases was hastily developed. Thus, on 1 November 1943 the US Fifteenth Air Force was formed to conduct the daylight bombing offensive against strategic targets in southern Germany and across South-Eastern Europe.

Key among which were the Rumanian oilfields and traffic along the River Danube. This new formation was joined by the smaller, but highly effective 205 Group, RAF that was trained and equipped for night bombing so mirroring their equivalent British-based formations. The damaging attacks on the Reich's oil supplies and the hugely effective Danube mining campaign conducted at night by 205 Group delivered huge strategic effect. The latter reduced vital oil and goods traffic into the Reich to a trickle but also dislocated the supply and logistics train into the southern part of the Eastern Front so giving manifest support to the Soviets. In this volume the early months of this hugely significant air campaign are described in minute detail, including the actions of Germany's Axis allies such as Hungary, Rumania and Bulgaria that were encountered for the first time by the Western Allies. Description of the strategic bomber campaign in the Mediterranean theatre will conclude in Volume Seven.