This fort was probably founded after the capture of neighbouring Sas van Gent by the States in 1644 and before the signing of the Peace of Munster in 1648. It thus became a kind of Spanish counter fort to the west of Sas van Gent. The name is derived from archduke Leopold Wilhelm, governor of the Southern Netherlands from 1647 to 1656. This is one of the last forts to be founded during the Eighty Years’ War and is similar to Fort Francipani. However, its shape is simpler: a trapezium shaped fort surrounded by an inner moat, a glacis and an outer moat. The corner points of the glacis were 200 m away from each other. Not much remains, but to the south of Staakstraat (= the Oude Graaf Jansdijk), the glacis is still recognisable in the form of the field. The ditch around the field follows the course of the earlier outer moat.