On 20 June oil targets were made third priority below the German aircraft industry and lines of communication between Germany and the armies at the front.

[9] Although the Butt Report of August 1941 identified the poor accuracy and performance of RAF bombing at the time,[7]: 70–71  Air Chief Marshal Charles Portal maintained at the 1943 Casablanca Conference the great importance of oil targets in Axis territory.

In March 1944 the "Plan for Completion of Combined Bomber Offensive" was put forward which found favour with the British Ministry of Economic Warfare.

[17] In June 1944, in response to Air Ministry query on resources, Bomber Command staff estimated it would take 32,000 tons of bombs to destroy 10 oil targets in the Ruhr.

They were deemed to be of such importance that one raid was staged that consisted only of bomb carrying fighters, to rest the bomber crews and surprise the defenders.

Even with the weather limitations: "This was the big breakthrough ... a plant would be wounded ... by successive attacks on its electrical grid—its nervous system—and on its gas and water mains."

[26] Despite its successes, by the spring of 1944 the Combined Bomber Offensive had failed to dislocate the German economy or inflict severe disruptions in the production of vital items; the oil campaign missions were the first targeted attacks to accomplish these goals.

Adolf Galland,[b] wrote in his book "the most important of the combined factors which brought about the collapse of Germany",[29] and the Luftwaffe's wartime leader, Hermann Göring, described it as "the utmost in deadliness".

[31] Luftwaffe Field Marshal Erhard Milch, referring to the consequences of the oil campaign, claimed that "The British left us with deep and bleeding wounds, but the Americans stabbed us in the heart.

Working from German records for certain sites, the USSBS determined that on average 87% of Allied bombs fell outside the factory perimeter and that only a few percent struck plant or equipment inside the boundary.