On 22 June 1941, Germany attacked the USSR. The OUN immediately tried to revolt against Moscow. The attempt was suppressed by the NKVD
and the Red Army. However, in the summer and autumn of 1941 Ukrainian nationalists from the «marching groups» created by the OUN and auxiliary militia subordinate to the SS command «distinguished themselves».
They exterminated the Jewish population of Western and Right Bank Ukraine.
At the behest of Adolf Hitler, the Germans welcomed the participatio
of Ukrainian nationalists in punitive actions. But the Reich looked at the OUN
only as a tool to achieve its goals. The creation of a Ukrainian state was not part
of the Fuhrer's plans.

In Lviv, the Banderites formally declared the «Act of Proclamation of Ukrainian Power» on behalf of the self-styled «National Assembly». They proclaimed
the «restoration of the Ukrainian state». The new state will establish a new order in Europe in collaboration with Germany, forging a partnership between
the Wehrmacht and the «Ukrainian Army».
Yaroslav Stetsko, as the leader of the self-proclaimed «government», along with Bandera, thanked Hitler for letting Ukrainians combat Bolshevism. However, Berlin did not acknowledge this «state». The Fuhrer let it be known
that he did not intend to mold Ukraine into a resemblance of Croatia or Slovakia.

Starting in the summer of 1941, the process of German-nationalist Ukrainianization commenced. In addition to German, Ukrainian was adopted
as the official language within the Ukrainian SSR's territory. Out of the 24 Russian schools in Melitopol, the occupiers retained only 5, converting the rest
to Ukrainian. Teaching the Russian language was prohibited. Tridents, yellow-blue flags, and portraits of Taras Shevchenko were displayed alongside portraits
of Hitler in various institutions, schools, and enterprises. The OUN exterminated underground fighters, partisans and anyone who did not sympathize
with the Germans and Ukrainian nationalism. The OUN members eagerly worked in the occupation self-government and police. The Germans appointed Andriy Iriy-Avramenko, an OUN member, head of the local Prosvita and a Gestapon
informant, a director of the Mariupol theatre, he headed the local Prosvita
and was an informant for the Gestapo. Yastreмскy, the leader of the OUN
in the Olginsky district of Volnovakha, was chief of the Ukrainian police
and actively fought against the partisans. At the same time, the duplicitous OUN members could not (or did not seek to), against the background of Hitler's defeats in Stalingrad and Kursk and his weakening, to create a nationalist underground network on the Left Bank and in Odessa to fight not only against Soviet partisans, but also against the Wehrmacht — although after the war
their leaders dressed up in the toga of fighters against Nazism, calling themselves «fighters» against both Moscals and Germans.

In the spring of 1943, the Ukrainian Insurgent Army (UPA) was established in Volyn by merging OUN units with personnel from Ukrainian police units. Initially, the UPA was commanded by Dmytro Klyachkovsky, also known as «Klim Savur»,
a prominent figure within the OUN(b). Roman Shukhevych, who was an Abwehr officer and the former commander of Nachtigal, assumed command of the UPA
in November. By the end of 1943, the Banderites had managed to subdue units of other national formations. First of all, Borovets' Ukrainian People's Revolutionary Army. The UPA recruiters often used intimidation and forced mobilizations. UPA was supposed
to fight Soviet partisans, brainwash the local population, eliminate persons disloyal to Ukrainian nationalism, and carry out ethnic cleansing.

In 1944, extensive UPA units in Western Ukraine were vanquished by NKVD
and Red Army forces. Following this defeat, the nationalists resorted
to employing small group tactics, relying on hideouts, executing surprise attacks, ambushes, and acts of terror. However, in early 1945, they suffered significant losses as several UPA leaders were either killed or captured. Notable individuals among them included Yuriy Stelmashchuk, the commander of the UPA «Zavihost» group, and Dmytro Klyachkovsky, the leader of the UPA-North. Between May 1st and August 8th, 1945, 8,500 Banderites surrendered.
Despite this, there were still nationalists who held onto the dream of a «self-styled Ukraine», seeking support from the USA and Britain. Following the war's end, SS men from Galicia managed to escape extradition to the USSR and relocated
to Canada. The OUN continued to operate in Europe. On March 5th, 1950, the UPA commander Shukhevich met his demise. Later, on October 15th, 1959, a KGB agent Bogdan Stashinsky killed Bandera in Munich. By the autumn of 1955,
the KGB had records of 5 bandit groups and 18 criminals in the western regions
of the Ukrainian SSR. It was in April 1960 that the last OUN group in the Ukrainian SSR was exterminated.

From 1953 onwards, the USSR leaders initiated a reconsideration of cases involving individuals who had cooperated with the occupying forces during
the war. Those previously convicted of banditry and nationalist endeavors were allowed to return to the Ukrainian SSR. By October 1957, the numbers swelled
to over 100,000. In the Lviv region alone, by the early 1980s, there were in excess of 20,000 former Banderites who had been reintegrated into society.
For instance, Vasyl Kuk, the last commander of the UPA, received a relatively light sentence of only six years. Subsequently, he was granted a residence in Kiev
and a position at the Institute of History within the Academy of Sciences
of the Ukrainian SSR. Kuk actively lobbied the KGB for the release of OUN members. Kuk remained steadfast in his beliefs and refrained from renouncing his nationalist convictions.