Slovak invasion of Poland in the context of Slovak Republic (1939-1945)

The Second Polish Republic, officially known at the time as the Republic of Poland, was a country in Central and Eastern Europe that existed between 7 October 1918 and 6 October 1939 after being established in the final stage of World War I. The Second Republic was taken over in 1939, after it was invaded by Nazi Germany, the Soviet Union, and the Slovak Republic, marking the beginning of the European theatre of the Second World War. The Polish government-in-exile was established in Paris and later London after the fall of France in 1940.

When, after several regional conflicts, most importantly the victorious Polish-Soviet war, the borders of the state were finalized in 1922, Poland's neighbours were Czechoslovakia, Germany, the Free City of Danzig, Lithuania, Latvia, Romania, and the Soviet Union. It had access to the Baltic Sea via a short strip of coastline known as the Polish Corridor on either side of the city of Gdynia. Between March and August 1939, Poland also shared a border with the then-Hungarian governorate of Subcarpathia. In 1938, the Second Republic was the sixth largest country in Europe. According to the 1921 census, the number of inhabitants was 25.7 million. By 1939, just before the outbreak of World War II, this had grown to an estimated 35.1 million. Almost a third of the population came from minority groups: 13.9% Ukrainians; 10% Ashkenazi Jews; 3.1% Belarusians; 2.3% Germans and 3.4% Czechs and Lithuanians. At the same time, a significant number of ethnic Poles lived outside the country's borders.

Slovakia, officially the (First) Slovak Republic, and from 14 March until 21 July 1939 officially known as the Slovak State (Slovak: Slovenský štát), was a partially recognized clerical fascist client state of Nazi Germany which existed between 14 March 1939 and 4 April 1945 in Central Europe. The Slovak part of Czechoslovakia declared independence with German support one day before the German occupation of Bohemia and Moravia. It controlled most of the territory of present-day Slovakia, without its current southern parts, which were ceded by Czechoslovakia to Hungary in 1938. The puppet state was the first formally independent Slovak state in history. Bratislava was declared the capital city.

A one-party state governed by the far-right Hlinka's Slovak People's Party, the Slovak Republic is primarily known for its collaboration with Nazi Germany, which included sending troops to the invasion of Poland in September 1939 and the Soviet Union in 1941. In 1940, the country joined the Axis when its leaders signed the Tripartite Pact.