 Complete the following phrase:  The oil campaign over Romania and against the synthetic oil plants in the Ruhrin which most oilfields had been destroyed, captured or damaged by 1945triggered a critical fuel shortage from the autumn of 1944 onwards which denied the Luftwaffe the resources to capitalise on its numerical strength. Paradoxically, production was able to replace the relatively small losses and operational serviceability reached an all-time high since ground crews had more opportunity to work on machines. The Luftwaffe was still capable of taking a toll on Bomber Command on occasion, but unless more powerful radars and communications could be introduced in time it was doubtful British air superiority at night could be challenged. The impotence of the night fighter force as an organisation was demonstrated during the 