sentences:  The official designation of the latter was "Cartridge, Mortar, 4.2-inch".Mustard gas was not used in these wars and the U.S. ended up with a large number of these shells, declaring over 450,000 of them in stockpile in 1997 when the Chemical Weapons Treaty came into force.Destruction efforts to eliminate this stockpile are continuing with a few of these aged shells occasionally found to be leaking.