The Siege of Leiden took place from 1574 to 1575 during the Eighty Years' War, a conflict between the Dutch provinces and Spanish rule. The city of Leiden, located in the Netherlands, was surrounded by Spanish forces led by Francisco de Valdez. The siege aimed to suppress the Dutch revolt against Spanish authority. To break the siege, the Dutch leaders, including William of Orange, devised a plan to flood the surrounding area. In April 1575, they opened the dikes, allowing water to inundate the land and forcing the Spanish troops to retreat. This victory was crucial for the Dutch struggle for independence.