The Chemical Mortar Battalion was an army unit attached to the U.S. infantry division during World War II. Their name comes from the 4.2 inch chemical mortars they were armed with. These weapons were highly explosive alongside releasing other types of chemical warfare, like gas, fire, or smoke. They did not act as combat units alone. Instead, these battalions supported combatant infantry divisions. Oftentimes, mortar battalion units remained on the frontline while infantry divisions rotated out because they were so valuable to the battle.