Although the
Butt Report of August 1941 identified the poor accuracy and performance of RAF bombing at the time, The first US bombing of a European target was of the
Ploiești refineries in Romania on 12 June 1942 and the oil campaign continued at a lower priority until 1944. Priority fell with the need for attacks on German
V-weapon targets ("
Operation Crossbow") in France and then the attacks on lines of communication in preparation for the invasion of France (described as the "
Transportation Plan"). in
Romania burning after the raid of B-24 Liberator bombers in
Operation Tidal Wave In March 1944 the "Plan for Completion of
Combined Bomber Offensive" was put forward which found favour with the British
Ministry of Economic Warfare. The plan proposed attacking "fourteen synthetic plants [of
Brabag ] and thirteen refineries" of Nazi Germany. The plan estimated Axis oil production could be reduced by 50% by bombing—33% below the amount Nazi Germany needed—but also included 4 additional priorities: first oil, then fighter and ball bearing production, rubber production, and bomber output. The damage caused by the 12 and 28 May trial bombings of oil targets, as well as the confirmation of the oil facilities' importance and vulnerability from
Ultra intercepts and other intelligence reports, would result in the oil targets becoming the highest priority on 3 September 1944. 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. Air Chief Marshal
Arthur Harris agreed to divert spare effort to oil targets. 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. However, due to bad fall and winter weather, a "far greater tonnage" was expended on
Transportation Plan targets than oil targets. The benzol (oil) plant at
Linz in
Austria was bombed on 16 October 1944. In January 1945, the priority of oil targets was lowered. To prevent oil supplies from Romania reaching Germany, the RAF had extended its aerial mining activities to the Danube. ==Post-war==