Defense line

The Victoria Lines, a line of fortification in Malta built to divide the sparsely populated north of the island from the densely populated south

Defense line or fortification line is a geographically-recognizable line of troops and armament, fortified and set up to protect a high-value location during an armed conflict.

Such a line may be based on natural terrain features related to difficult terrain, such as rivers or marshes; temporary field fortification such as trenches; and more permanent fortifications such as fortresses.

World-famous fortification lines include Maginot Line in France.