Chemical mortar battalion

The United States chemical mortar battalions were army units attached to U.S. infantry divisions during World War II. They were armed with 4.2 in (107 mm) chemical mortars. For this reason they were also called the "Four-deucers".

Originally, chemical mortar battalions consisted of a headquarters company and four mortar companies. In 1943, this "square" organization was modified to three mortar companies for a better fit with the three infantry regiments of the "triangular" infantry divisions.

Per Table of Organization and Equipment 3-25 of 29 September 1944, a typical chemical mortar battalion had an establishment of 37 officers, 138 NCOs and 481 junior enlisted men not counting the attached medical detachment. It consisted of:

A chemical mortar company usually had an establishment of 9 officers, 40 noncommissioned officers and 118 junior enlisted men. It consisted of:

A mortar platoon consisted of:

Chemical mortar battalions were not assigned as integral parts of divisions or other units. As other units went into combat, chemical mortar battalions were attached to them as support. In 1943, General Mark Clark's Fifth Army established a policy that no infantry division would be committed to combat without a chemical mortar battalion attached. As a result, when infantry units were rotated out of combat, the mortar battalions often stayed in the line and were attached to the fresh infantry unit. Chemical mortars were in such high demand that often the companies of a battalion would be split up and assigned to different divisions. Two Fifth Army antiaircraft battalions were retrained as chemical mortar battalions (99th and 100th) On the first day that General George Patton's Third Army became operational, in the summer of 1944, he issued a standing order to his staff that no infantry division would be committed to combat without a chemical mortar battalion attached, and no infantry regiment would be committed without a mortar company attached.

During World War II, 25 chemical mortar battalions were sent overseas:

Seven additional battalions (the 443rd, 483rd, 534th, 537th, 560th, 781st and 782nd) were converted from field artillery battalions during the war, but were activated too late to serve overseas.

After World War II, the U.S. War Department transferred the operations and development of chemical mortars to the Ordnance Department, in this way making the mortar an official infantry weapon.

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