Nachtigall Battalion
The Nachtigall Battalion (English: Nightingale Battalion), also known as the Ukrainian Nightingale Battalion Group (German: Bataillon Ukrainische Gruppe Nachtigall), or officially as Special Group Nachtigall (German: Sondergruppe 'Nachtigall')
was a subunit under command of the German Abwehr special-operations unit  Lehrregiment "Brandenburg" z.b.V. 800 in 1941. Along with the Roland Battalion it was one of two military units which originated on February 25, 1941, when the head of the Abwehr, Admiral Wilhelm Franz Canaris, sanctioned the formation of a "Ukrainian Legion" under German command. The Legion was composed of volunteer Ukrainians many of whom were members or supporters of Organization of Ukrainian Nationalists (OUN-B). The Battalion participated in early stages of Operation Barbarossa (the  Axis invasion of the Soviet Union) with Army Group South
between June and August 1941.