The second Schweinfurt raid, also called Black Thursday, was a World War II air battle that took place on 14 October 1943, over Nazi Germany between forces of the United States 8th Air Force and German Luftwaffe fighter arm (Jagdwaffe). The American bombers conducted a strategic bombing raid on ball bearing factories to reduce production of these vital parts for all manner of war machines. This was the second attack on the factories at Schweinfurt. American wartime intelligence claimed the first Schweinfurt–Regensburg mission in August had reduced bearing production by 34 percent but had cost many bombers. A planned follow-up raid had to be postponed to rebuild American forces. As the squadrons rebuilt, plans for the return mission were modified based on the lessons learned. Planners added additional fighter escorts to cover the outward and return legs of the operation and sent the entire force against Schweinfurt alone, instead of splitting the force. Despite these changes, a series of minor mishaps combined with the ever-increasing efficiency of the German anti-aircraft effort proved to be devastating. Of the 291 B-17 Flying Fortresses sent on the mission, 60 were lost, another 17 damaged so heavily that they had to be scrapped and another 121 had varying degrees of battle damage. Losses represented over 26 percent of the attacking force and losses in aircrew were equally severe, with 650 men lost of 2,900, 22 percent of the bomber crews. The American Official History of the Army Air Forces in the Second World War acknowledged losses had been so great that the USAAF would not return to the target for four months, "The fact was that the Eighth Air Force had for the time being lost air superiority over Germany". The operation was a failure. The bomber formations were left exposed to attacks by German fighters and the faulty preparations for the creation of reserves in the summer of 1943 meant that such costly operations could not be sustained. An escort of 24 squadrons of Spitfires equipped with drop tanks was provided on the first and last leg of the mission. The strategy of the Allied air forces was flawed. Arthur Harris, Air Officer Commanding RAF Bomber Command questioned the intelligence that claimed ball bearings to be vital to the German war economy. Harris refused to cooperate with the Americans, believing ball bearing targets to be a "panacea". Post-war analysis has shown Harris's objections