in military science, a blockhouse is a small fortification. it usually has one or more rooms with loopholes, allowing its defenders to fire rifles or handguns in various directions. it usually refers to an isolated fort in the form of a single building. it serves as a defensive strong point against any enemy that does not possess siege equipment or, in modern times, artillery. a fortification intended to resist these weapons is more likely to qualify as a fortress or a redoubt.