The M556 Counter Defilade Grenade Launcher is a UNSC infantry weapon frequently utilized to kill or injure hostile forces sheltered behind or in cover inaccessible by normal infantry weaponry (i.e. foxholes, trenches, concrete barriers). As its name suggests, it fires airbursting 25mm grenades, fused to explode above and slightly behind the target's position, a feature which makes it extremely effective when used against light-armoured infantry.