The Hel (German: Hela) Peninsula was part of Prussia and then Germany from 1772 until 1919. After the peninsula became part of the Second Polish Republic after World War I, it acquired considerable military significance (Polish Corridor), and was turned into a fortified region, with a garrison of about 3,000. In the course of the Battle of Hel in 1939, Polish forces dynamited the peninsula at one point, turning it into an island.