World War II: About 3,000 Polish Army troops began a nearly month-long defence of the Hel Peninsula during the German invasion of Poland.

World War II or the Second World War was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

The Land Forces are the land forces of the Polish Armed Forces. They currently contain some 110,000 active personnel and form many components of the European Union and NATO deployments around the world. Poland's recorded military history stretches back a millennium – since the 10th century. Poland's modern army was formed after Poland regained independence following World War I in 1918.

The Battle of Hel was a World War II engagement fought from 1 September to 2 October 1939 on the Hel Peninsula, of the Baltic Sea coast, between invading German forces and defending Polish units during the German invasion of Poland. The defense of the Hel Peninsula took place around the Hel Fortified Area, a system of Polish fortifications that had been constructed in the 1930s near the interwar border with the German Third Reich.

Hel Peninsula is a 35-kilometre-long (22 mi) sand bar peninsula in northern Poland separating the Bay of Puck from the open Baltic Sea. It is located in Puck County of the Pomeranian Voivodeship.