Operation Ostra Brama
Operation Ostra Brama (lit.
Operation Sharp Gate) was an armed conflict during World War II between the Polish Home Army and the Nazi German occupiers of Vilnius (Polish: Wilno). It began on July 7, 1944, as part of a Polish national uprising, Operation Tempest, and lasted until July 14, 1944. Though the Germans were defeated, the following day the Soviet Red Army entered the city and the Soviet NKVD proceeded to intern Polish soldiers and to arrest their officers. Several days later, the remains of the Polish Home Army retreated into the forests, and the Soviets were in control of the city.
There are some controversies involved in determining the result of the battle. From the Polish point of view, while the German defeat constitutes a Polish tactical victory, the ensuing destruction of the Polish units by the Soviets resulted in a strategic defeat, especially considering the goals of Operation Tempest. From the Soviet point of view, the operation was a complete success, as both the Germans and the Poles loyal to the London government suffered a defeat.
On June 22, 1944, the Soviets launched their main summer offensive (Operation Bagration) in Belarus. Involving 2.5 million soldiers and over 6,000 tanks, the offensive sought to destroy Army Group Center while also preventing the Germans from diverting troops to combat the Allied landings in France. In the ensuing battle, the Wehrmacht suffered one its worst defeats of the war as Army Group Center was shattered and Minsk liberated.
BBC - History: World War Two