Operation Tidal Wave was an air attack by bombers of the United States Army Air Forces based in Libya on nine oil refineries around Ploiești, Romania on 1 August 1943, during World War II. It was a strategic bombing mission and part of the "oil campaign" to deny petroleum-based fuel to the Axis. The mission resulted in "no curtailment of overall product output", and so was unsuccessful.. This mission was one of the costliest for the USAAF in the European Theater, with 53 aircraft and 660 aircrewmen lost. It was the worst loss ever suffered by the USAAF on a single mission, and its date... was later referred to as "Black Sunday". Five Medals of Honor and numerous Distinguished Service Crosses were awarded to Operation Tidal Wave crew members. Romania had been a big participant in the oil industry since the 1800s. It was one of the largest producers in Europe and Ploesti was a major part of that production. . In 1943, crude and refined oil from the Ploiești oil fields provided about 35% of all Axis oil supplies. In June 1942, 13 B-24 Liberators of the "Halverson project" attacked Ploiești.
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