The Stokes mortar was a British trench mortar designed by Sir Wilfred Stokes KBE that was issued to the British and U.S. armies, as well as the Portuguese Expeditionary Corps, during the latter half of the First World War. The 3-inch trench mortar is a smooth-bore, muzzle-loading weapon for high angles of fire. Although it is called a 3-inch mortar, its bore is actually 3.2 inches or 81 mm.