Anti-Soviet resistance by the Ukrainian Insurgent Army

The Ukrainian Insurgent Army (UPA) waged a guerrilla war against the Soviet Union in the western regions of the Ukrainian SSR and southwestern regions of the Byelorussian SSR during and after World War II. With the Red Army forces successful counteroffensive against the Nazi Germany and their invasion into western Ukraine in July 1944, UPA resisted the Red Army's advancement with full-scale guerrilla war, holding up 200,000 Soviet soldiers, particularly in the countryside, and was supplying intelligence to the Nazi Sicherheitsdienst (SD) security service. One major UPA victory against the Soviet Union was the killing of a high ranking Soviet General Nikolai Vatutin.

Source: Wikipedia — Anti-Soviet resistance by the Ukrainian Insurgent Army (CC BY-SA 4.0)