'Regenfass' was a German operation against partisans in the Ushachy region of Belorussia to the south of Polotsk in the German-occupied western USSR (April 1944).

The region was held by Generaloberst Georg-Hans Reinhardt’s 3^rd Panzerarmee of Generalfeldmarschall Walter Model’s Heeresgruppe 'Mitte' and, being earmarked for recapture in the 'Siauliai Offensive Operation' within 'Bagration' by General Hovhannes Kh. Bagramyan’s 1^st Baltic Front in July 1944, was thus a primary area for partisan activities.