In the midst of the Sicilian campaign, on 1 August 1943, Mediterranean-based heavy bombers executed one of the outstanding air operations of World War II. This was the low-level B-24 attack on the Ploesti oil refineries in Romania - the first large-scale, minimum-altitude attack by Army Air Forces (AAF) heavy bombers upon a strongly defended target and the longest major bombing mission, in terms of distance from base to target, undertaken up to that time.