fortification
n.a strong building or wall built to protect a place from enemies. It can also mean the act of making a place stronger to defend it.
n.a structure or system of structures designed to protect a location from attack; the act of reinforcing a position with defensive works.
“The city built a new fortification to keep out the invaders.”
“Historians studied the medieval fortification to understand how the castle withstood the siege for three months.”
“The strategic placement of the fortification allowed the defenders to control the narrow mountain pass and prevent any large-scale movement of enemy troops.”
“Trebuchets and other siege engines (we will, under no circumstances, be delving into the distinctions between the different types of catapults ) were meant to take out walls and other fortifications.”
“The site was particularly compelling because it contained an undisturbed trench, a part of Fort Mercer’s fortifications.”
Borrowed from Middle French fortification, from Late Latin fortificatio, fortificationem, from fortifico, from Latin fortis. By surface analysis, fort + -ification.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.