British iron mortar, circa 1810

Caption: British iron mortar, circa 1810

Mortars were designed to shoot an exploding shell at a very high angle, 45 degrees or more. They were used in the siege and defence of fortifications. An explosive shell fired into the air, curved to drop within the defenses of the enemy. When the shell's fuse burned down, it exploded. These projectiles are the 'bombs bursting in air' mentioned in the American national anthem, where they were being fired from the British fleet attacking Baltimore.