OUN-B, or the Organization of Ukrainian Nationalists - Bandera faction, was a nationalist political and paramilitary group in Ukraine during the mid-20th century. It emerged from the broader OUN movement, which sought Ukrainian independence from Soviet and Polish control. OUN-B was named after its leader, Stepan Bandera, and was known for its radical approach to achieving its goals. The group played a significant role during World War II, collaborating with Nazi Germany at times, but later opposing them as the war progressed. OUN-B's actions and ideology have been subjects of controversy, particularly regarding their involvement in ethnic violence and their stance on Ukrainian nationalism.