During the latter half of 1944, the bombing of German-held oil facilities became a major priority of the offensive. On 27 August, a force of 216 Halifax bombers, alongside smaller numbers of de Havilland Mosquitos and Lancasters and a sizable escort of Supermarine Spitfires, conducted the first major daylight operation by Bomber Command against a target inside Germany that year, attacking the oil refinery at Homberg on the Ruhr. In spite of heavy fire from anti-aircraft defenses, no bombers were downed and the refinery was severely damaged in places. Attacks upon oil production facilities throughout Germany would become commonplace within the remaining months of the war.