Bridgehead

A bridgehead (or bridge-head) is the strategically important area of ground around the end of a bridge or other place of possible crossing over a body of water which at time of conflict is sought to be defended/taken over by the belligerent forces.

Bridgeheads typically exist for only a few days, the invading forces either being thrown back or expanding the bridgehead to create a secure defensive lodgement area, before breaking out into enemy territory, such as when the U.S. 9th Armored Division seized the Ludendorff Bridge at Remagen in 1945 during World War II. In some cases a bridgehead may exist for months.