||The high cost of the Allied air offensive during World War II.On August 29, 1944, the 15th U.S. Army Air Force unleashed 500 bombers against oil and rail targets throughout central Europe. It dispatched the 20th Squadron of the 2nd Bombardment Group on what they regarded as an easy assignment: attack the Privoser Oil Refinery and associated railroad yards at Moravska Ostrava, Czechoslovakia. This "milk run" deteriorated into the bloodiest day in the 2nd Bombardment Group's history: not a single one of the 20th Squadron's B-17 Flying Fortress bombers returned from the mission. Forty airmen were killed, another 46 spent the rest of the war as POWs, and only four, with the aid of the OSS and anti-German partisans, and sympathetic Czech civilians managed to evade capture.The ninety airmen on the mission to Moravska Ostrava provide a remarkable personal window into the Allies' Combined Bomber Offensive at its height during WWII. In a microcosm, their stories encapsulate how the U.S. Army Air Forces built, trained, and employed one of the mightiest war machines ever seen. Their stories also illustrate, however, the terrible cost in lives demanded by that same machine.