The Soviet invasion of Poland began on September 17, 1939. Meanwhile the German Army attack on Poland had already started on September 1, triggering World War II. This two-front military campaign had been agreed upon three weeks before in the Molotov-Ribbentrop Pact signed on August 23, 1939. The cause of this Soviet military campaign was the Polish attack and occupation of Soviet territory in Ukraine and Belorussia (Belarus) in 1919, causing the Polish-Soviet War. Backed by Great Britain, France, and the USA, Poland had won this war in 1920, depriving the Soviet Union of western portions of Belarus and Ukraine.
For the invasion of Poland, the Red Army deployed seven field armies, which were arranged around two Fronts (the equivalent of Army Groups). The Belorussian Front included the 10th, 3rd, and 11th Army, being under the overall command of M.P. Kovalov. Meanwhile, the Ukrainian Front was made up of the 5th and the 6th Army and they were led by Semyon Timoshenko. Both military Fronts totaled 450,000 men, with more than 3,100 tanks and armored vehicles. They were better equipped and accoutered than the Polish soldiers.
The Soviet military campaign in Poland was carried out with relative ease as the Wehrmacht had lured and drawn most of the Polish Army’s military units. The Red Army encountered only isolated defending forces, which were defeated and crushed in two weeks. The Belorussian Front invaded the northeastern portion of Poland, while the Ukrainian Front forces attacked across the southeastern part of this country. They met little organized resistance. The only important military engagement was the battle for the city of Lvov, which took place on September 22. By October 6, the Soviet forces had already met their German counterparts, with their officers shaking hands, as the last pocket of Polish resistance had been snubbed out.
Below, map showing the advance of the two Soviet Fronts in Poland in September 1939.
