Invasion of Poland (1939) in the context of "German–Soviet Boundary and Friendship Treaty"

The German–Soviet Boundary and Friendship Treaty was a second supplementary protocol of the Molotov–Ribbentrop Pact of 23 August 1939. It was a secret clause as amended on 28 September 1939 by Nazi Germany and the Soviet Union after their joint invasion and occupation of sovereign Poland. It was signed by Joachim von Ribbentrop and Vyacheslav Molotov, the foreign ministers of Germany and the Soviet Union respectively, in the presence of Joseph Stalin. Only a small portion of the protocol, which superseded the first treaty, was publicly announced, while the spheres of influence of Nazi Germany and the Soviet Union remained secret. The third secret protocol of the Pact was signed on 10 January 1941 by Friedrich Werner von Schulenburg and Molotov, in which Germany renounced its claims on a part of Lithuania, west of the Šešupė river. Only a few months after this, Germany started its invasion of the Soviet Union.

In the aftermath of the German and Soviet invasion of Poland, which took place in September 1939, the territory of Poland was divided between Nazi Germany and the Soviet Union. The Soviets had ceased to recognise the Polish state at the start of the invasion. Since 1939 German and Soviet officials coordinated their Poland-related policies and repressive actions. For nearly two years following the invasion, the two occupiers continued to discuss bilateral plans for dealing with the Polish resistance during Gestapo-NKVD Conferences until Germany's Operation Barbarossa against the Soviet Union, in June 1941.

The Molotov–Ribbentrop Pact was broken and the new war erupted, the Soviets had already arrested and imprisoned about 500,000 Polish nationals in the Kresy macroregion including civic officials, military personnel and all other "enemies of the people" such as clergy and the Polish educators: about one in ten of all adult males. There is some controversy as to whether the Soviet Union's policies were harsher than those of Nazi Germany until that time. An estimated 150,000 Polish citizens were killed by Soviet repressions.

Władysław Bortnowski (12 November 1891 – 21 November 1966) was a Polish historian, military commander and one of the highest ranking generals of the Polish Army. He is most famous for commanding the Pomorze Army in the Battle of the Bzura during the invasion of Poland in 1939. He is also notable for serving as president of the Józef Piłsudski Institute of America between 1961 and 1962.

The Warsaw Army (Polish: Armia Warszawa) was one of the Polish armies to take part in the Polish Defensive War of 1939. Created on 8 September, eight days after the invasion begun, it was an improvised formation charged with the defence of the Polish capital of Warsaw (Warszawa).

Wizna [ˈvizna] is a village in Łomża County of Podlaskie Voivodeship, in north-eastern Poland, situated on the Narew River. Wizna is known for the battle of Wizna which took place in its vicinity during the 1939 Invasion of Poland at the start of World War II.

Farming and food production are the primary sources of income for the residents. The food production by private farms provides favorable conditions for the development of processing industry.

The Pomeranian Voivodeship or Pomorskie Voivodeship (Polish: Województwo Pomorskie) was an administrative unit of Interwar-Poland (from 1919 to 1939). It ceased to function in September 1939, following the German and Soviet invasion of Poland.

Most of the territory of Pomeranian province became part of the current Kuyavian-Pomeranian Voivodeship, of which one of two capitals is the same as the interwar voivodeship's Toruń; the second one is Bydgoszcz.