Invasion of Poland

The invasion of Poland was a massive military campaign that began World War II.

This conflict, also called the September Campaign, involved a joint attack on the Republic of Poland. Nazi Germany, the Slovak Republic, and the Soviet Union all participated in the invasion. The primary goal was to end Poland's existence as a sovereign nation. The attackers intended to divide the country and its people among themselves. This period of intense fighting lasted from September 1 to October 6, 1939.

The invasion followed years of rising tensions and aggressive diplomacy.

Adolf Hitler, the leader of Nazi Germany, wanted to expand German territory. He specifically targeted the Free City of Danzig and the Polish Corridor. The Corridor was a strip of land that had been part of Poland since the Treaty of Versailles. The city of Danzig had a German majority and was a nominally independent area. Hitler used these territorial disputes as a casus belli, or a reason for war. He claimed that Germans in Poland were being persecuted to justify his actions.

Before the fighting started, Germany and the Soviet Union made a secret agreement.

This was the Molotov–Ribbentrop Pact, signed on August 23, 1939. The pact included a secret protocol to divide Eastern Europe into spheres of influence. Germany was to take the western third of Poland. The Soviet Union was to take the eastern two-thirds. This agreement meant that Germany would not have to worry about Soviet opposition during its attack. It effectively cleared the way for the German military to move against Poland.

The military campaign unfolded in several rapid and difficult stages.

On September 1, 1939, German and Slovak forces invaded from the north, south, and west.

Polish forces initially withdrew from the borders to established defense lines in the east. They attempted to hold a position known as the Romanian Bridgehead. They hoped to receive relief from their allies, France and the United Kingdom. On September 3, the United Kingdom and France declared war on Germany. However, the actual military aid that reached Poland was very limited.

The situation became impossible for Poland when a second front opened.

On September 17, the Soviet Red Army invaded Eastern Poland. This invasion followed the territory beyond the Curzon Line. The Soviet move rendered the Polish defensive plans obsolete. Facing two massive armies, the Polish government ordered an emergency evacuation to neutral Romania. The campaign finally ended on October 6 after the Battle of Kock. By this time, German and Soviet forces had gained full control over the country.

The invasion resulted in the total collapse of the Second Polish Republic.

Following the defeat, Germany annexed western Poland and the former Free City of Danzig. The remaining territory was placed under the administration of the General Government. The Soviet Union incorporated its new lands into the Byelorussian and Ukrainian republics. They immediately began a process of Sovietization in these areas. This reorganization changed the political map of Europe for the duration of the war.

Despite the military defeat, the Polish people did not stop fighting.

A collective of underground resistance organizations formed the Polish Underground State. These groups worked within the occupied territory to resist German and Soviet control. Many military members escaped the country to join the Polish Armed Forces in the West. These soldiers remained loyal to the Polish government-in-exile. Their continued resistance showed that while the land was occupied, the Polish state lived on through its people.