In military engineering and fortification, a distinction is made between a ditch and a trench. A ditch is a barrier, designed to slow down or break up an attacking force, while a trench is a cover, intended to provide protection to the defenders. In Medieval fortification, a ditch was often constructed in front of a defensive wall. When filled with water, such a defensive ditch is called a moat. Today ditches are of no importance as an obstacle for persons, but are still often used as anti-vehicle obstacles.