Organisation of Ukrainian Nationalists

The Organisation of Ukrainian Nationalists (OUN; Ukrainian: Організація українських націоналістів, romanized: Orhanizatsiya ukrayins'kykh natsionalistiv) was a Ukrainian nationalist organisation established in 1929 in Vienna, uniting the Ukrainian Military Organization with smaller, mainly youth, radical nationalist right-wing groups. The OUN was the largest and one of the most important far-right Ukrainian organizations operating in the interwar period on the territory of the Second Polish Republic.

The OUN was mostly active preceding, during, and immediately after the Second World War. Its ideology has been described as having been influenced by the writings of Dmytro Dontsov, from 1929 by Italian Fascism, and from 1930 by German Nazism. The Organization pursued a strategy of violence, terrorism, and assassinations with the goal of creating an ethnically homogenous and totalitarian Ukrainian state.

During the Second World War, in 1940, the OUN split into two parts. The older, more moderate members supported Andriy Melnyk's OUN-M, while the younger and more radical members supported Stepan Bandera's OUN-B. On 30 June 1941 OUN-B declared an independent Ukrainian state in Lviv, which had just come under Nazi Germany's control in the early stages of the Axis invasion of the Soviet Union. OUN-B pledged to work closely with Germany, which was described as freeing the Ukrainians from Soviet oppression, and OUN-B members subsequently took part in the Lviv pogroms. In response to the OUN-B declaration of independence, the Nazi authorities suppressed the OUN leadership. Members of the OUN took an active part in the Holocaust in Ukraine and Poland.

In October 1942 OUN-B established the Ukrainian Insurgent Army (UPA). In 1943–1944, in an effort to prevent Polish efforts to re-establish prewar borders, UPA units carried out massacres of Poles in Volhynia and Eastern Galicia.

In the course of the war, with the approaching defeat of Nazi Germany, the OUN-B changed its political image, exchanging fascist symbolism and totalitarianism for democratic slogans.

After World War II, the UPA fought Soviet and Polish government forces. In 1947, in Operation Vistula, the Polish government deported 140,000 Ukrainians as part of the population exchange between Poland and Soviet Ukraine. Soviet forces killed 153,000, arrested 134,000, and deported 203,000 UPA members, relatives, and supporters.

During and after the Cold War, Western intelligence agencies, including the CIA, covertly supported the OUN. A contemporary organization that claims to be the same Organization of Ukrainian Nationalists is still active in Ukraine.