Boeing B-17 Flying Fortress Boeing B-17 Flying Fortress The Boeing B-17 Flying Fortress is a four-engined heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). Competing against Douglas and Martin for a contract to build 200 bombers, the Boeing entry (prototype Model 299/XB-17) outperformed both competitors and exceeded the air corps' performance specifications. Although Boeing lost the contract (to the Douglas B-18 Bolo) because the prototype crashed, the air corps ordered 13 more B-17s for further evaluation. From its introduction in 1938, the B-17 Flying Fortress evolved through numerous design advances, becoming the third-most produced bomber of all time,
World War II by country end of World War II until 1955, when the country again became a fully independent republic under the condition that it remained neutral. The four occupations zones were French, American, British, and Soviet, with Vienna also divided among the four powers. This paralleled the situation in post-war Germany. See East African Campaign (World War II). The British overseas territory of Gibraltar has been a British fortress and bulwark for over 300 years. From the first days of World War II, the Rock became a pivot of the Mediterranean, Operation Torch, the invasion of North Africa, was coordinated from the Rock.