West Belarus is the name used in reference to the territory of modern Belarus

Belarus

Belarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...

 which belonged to the Second Polish Republic

Second Polish Republic

The Second Polish Republic, Second Commonwealth of Poland or interwar Poland refers to Poland between the two world wars; a period in Polish history in which Poland was restored as an independent state. Officially known as the Republic of Poland or the Commonwealth of Poland , the Polish state was...

 between 1919 and 1939. The area of West Belarus was annexed into the Belarusian Soviet Socialist Republic following staged elections

Elections to the People's Assemblies of Western Ukraine and Western Belarus

Elections to the People's Assemblies of Western Ukraine and Western Belarus, which took place on October 22, 1939, were an attempt to legitimate territorial gains of the Soviet Union, at the expense of the Second Polish Republic...

 soon after the Nazi-Soviet Invasion of Poland in September . The corresponding terms of the Molotov–Ribbentrop Pact signed earlier in Moscow were broken, when the German army

Wehrmacht

The Wehrmacht – from , to defend and , the might/power) were the unified armed forces of Nazi Germany from 1935 to 1945. It consisted of the Heer , the Kriegsmarine and the Luftwaffe .-Origin and use of the term:...

 entered the Soviet occupation zone

Soviet occupation of Poland

Soviet occupation of Poland can refer to*Period from 1939 to 1941 - see Occupation of East Poland by Soviet Union*Period from 1945-1989 - see Northern Group of Forces...

 on June 22, 1941.