Traditionally, in the military, a mortar is a pipe in which a round (high explosive, phosphorous, or flare) fitted with a self-detonating charge is dropped in, and a firing mechanism at the bottom of the pipe launches the round in an arc-like trajectory. The paradox of mortar weapons is that all projectile weapons are limited to arc-traveling projectiles, except the mortar is a classification of which that arc is incredibly profound. This arc allows mortars to fire over obstacles that may stop normal weapons.