Polish Armed Forces in the East (Polish: Polskie Siły Zbrojne na Wschodzie) (or Polish Army in USSR) refers to military units composed of Poles created in the Soviet Union at the time when the territory of Poland was occupied by both Nazi Germany and the Soviet Union in the Second World War.
Broadly speaking, there were two such formations. The first was the Anders Army, created in the second half of 1941 and loyal to the Polish government-in-exile, after the German invasion of the USSR led to the Polish-Soviet Sikorski-Mayski Agreement declaring an amnesty for Polish citizens held captive in the USSR. In 1942 this formation was evacuated to Persia and transferred to the Western Allies, whereupon it became known as the Polish II Corps and went on to fight Nazi German forces in Italy, including at the Battle of Monte Cassino.
Following this, the remaining Polish forces in USSR were reorganised into a Soviet-controlled Polish I Corps in the Soviet Union, which in turn was reorganised in 1944 into the Polish First Army (Berling Army) and Polish Second Army, both part of the Polish People's Army (Ludowe Wojsko Polskie, LWP).
In 1944, the Polish People's Army was reorganised to become the military of the communist-ruled People's Republic of Poland.