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OUN-B was the militant wing of the Organization of Ukrainian Nationalists. It was founded in 1940 by Stepan Bandera, who was a leading figure in the Ukrainian independence movement. The OUN-B was responsible for a number of terrorist attacks, including the assassination of Polish President Ignacy Mościcki in 1939. After World War II, the OUN-B was active in the Ukrainian Insurgent Army, which fought against Soviet rule in Ukraine.