This article discusses several universal features of fortifications and distinguishes those features that are unequivocally military in function. The evidence adduced includes the features of known historic fortifications, relevant prescriptions by ancient military authors, and geometry. The archaeologically visible features that are universally used in military defenses are V-sectioned ditches, "defended" (especially baffled) gates, and bastions. It is also noted that ritual, ceremonial, or any other peaceful activities conducted within an enclosure having these architectural features does not preclude its obvious military function.