What is the military term for a narrow passageway through water or a valley on land?

In military parlance, a choke point (or chokepoint) is a geographical feature on land such as a narrow valley, a defile (narrow passage or gorge between mountains or hills), or it can be a bridge; it can also be a maritime passage through a critical waterway such as a strait, which forces an armed force to pass through in order to reach its objective.

A choke point can allow fewer defending forces to use the terrain as a force multiplier to thwart or ambush a much larger number of opponents. It prevents the attacker from advancing without first securing passage through the choke point.

The Strait of Gibraltar (picture) is an example of an important naval choke point, as entry into the Mediterranean Sea can be blocked by a small number of vessels. These straits along the Atlantic Ocean offers entry into the Mediterranean Sea between Spain and Morocco.

The Scottish knight Sir William Wallace (c. 1270 - 1305) became one of the main leaders during the First War of Scottish Independence. His victory over the English at the Battle of Stirling Bridge is another example of a choke point. In this battle, Wallace had a numerically inferior numbers (approximately 2,300) against the English army of about 9,000 to 12,000 men and the bridge collapsed during the battle.

In the Caribbean, there are many archipelagos that offered serveral maritime choke points that attracted pirates and buccaneers during the 17th and 18th centuries.