FORTS Fortification is military constructions and buildings designed for defense in warfare. Humans have constructed defensive work for many thousands of years, in a variety of increasingly complex designs. The term is derived from the Latin fortis (strong) and facere (to make). Large forts may class as fortresses, smaller ones often bore the name of fortalices. The word fortification is also referring to the practice of improving an areas defense with defensive work. City walls are fortifications but not necessarily called fortresses.