After the breakout of the German-Soviet war (1941-1945), the Wehrmacht troops soon made their way forward the territory of Ukraine. Western Ukraine was occupied by Nazis in the first weeks of war, and in July 1942 they took over all territory of Ukraine.
At first the Ukrainian people viewed the Germans as rescuers from the Stalin regime. The Organization of Ukrainian Nationalists (OUN) was of the same opinion and they saw Germany as their ally and the enemy of the Soviet Union.
On the eve of the German-Soviet war, administration of the OUN (with the assistance of German military officership that was rather loyal to Ukrainians) formed and trained two military units: “Nachtigall” and “Roland” battalions. They were supposed to participate in the fight with Bolsheviks as members of the Abwehr military intelligence. “Nachtigall” soldiers were the first to come to Lviv, so they took over all strategic places in the city. This enabled the OUN-B marching group to proclaim the Act of renewal of the Ukrainian State and to form Ukrainian State Administration – government headed by Yaroslav Stetsko. The Act was signed on June 30th, 1941, in Lviv. Nazis arrested administration of the OUN for refusing to cancel the Act. The leader of the OUN Stepan Bandera was sent to the German concentration camp Sachsenhausen, where he was kept until September 1944. Ukrainian officership of “Nachtigall” and “Roland” battalions were demanding to release Ya.Stetsko and S.Bandera. This caused withdrawal and disbandment of these military units in August 1941.