Main Page | See live article | Alphabetical index

Chemical mortar battalion

The United States chemical mortar battalions were army units attached to U.S. Infantry divisions, and it was their responsibility to service the 4.2" (107mm) chemical mortar during World War II. For this reason they were also called the "Four-deucers".

Table of contents
1 Chemical mortar battalions
2 The numbers of the battalions
3 What are chemical mortars?
4 The development and capabilities of the chemical mortar
5 When the mortar was adopted by the battalions

Chemical mortar battalions

A typical chemical mortar battalion had an establishment of 37 officers, 138 NCOs, and 481 junior enlisted men. It consisted of:

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

The numbers of the battalions

During World War II, there were a total of 25 chemical mortar battalions:

The 443rd, 483rd, 534th, 537th, 560th, 781st, and 782nd Battalions, although formed during the war, were activated too late to serve overseas. Most battalions, however, were active during the
Korean War

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

What are chemical mortars?

Chemical mortars are so named because of their capability of firing not only high explosive, but also chemical, gas, incendiary, and smoke marker shells. Chemical shells were on stand-by during World War II, to be used if enemy first-strike employment of chemical weapons demanded their application as a retaliatory means of action. It must be emphasized, however, that chemical shells were never used at any time by the US Army during World War II or any conflicts since, as enemy action never gave cause to their being utilized.

Chemical mortars, using high-explosive shells, came to be acknowledged by the U.S. Army command and army personnel as being one of the most effective means of striking at stationary targets, such as machine gun nests, prepared strong points, pillboxes, or even the powerful German 88mm guns. Another advantage chemical mortars offered, was their manoeuvrability, easy assembly, disassembly and reassembly from one location to another. The mortars were able to fire high-explosive shells from behind relatively concealed positions, such as natural escarpments on hillsides, or from woods. As their reputation of their devastating accuracy was spreading, the fluttering sound of a shell in transit, followed immediately by the huge thump of the explosion, tended to create panic among enemy forces who were subjected to their firepower.

The development and capabilities of the chemical mortar

The 4.2" chemical mortar was developed from the British World War 1 Stokes mortar that in its turn had evolved to prevail against the random effect of the gas clouds that in adverse weather would affect friend and foe alike with sometimes disastrous results in the trench-warfare conditions at the time.

A Stokes mortar could fire twenty shells a minute and had a range of 1100 yards and in this way was capable of overwhelming enemy trenches. The 4.2" mortar, that had by then a rifled barrel installed, and was firing shells with fins attached, had a range of 2300 yards by 1924. After modifying the bore, improving the two-legged support and the recoil mechanism, and producing barrels made of seamless nickel, the M1A1 model was capable of sending shells 2400 yards during the 1930s.
By 1942, after authorization had been sought and granted to use high explosive shells, again stronger barrels were being built into the new M2 model.

When the mortar was adopted by the battalions

In 1943, the mortar was adopted by the chemical mortar battalions. Later, it was developed to be capable of instantly firing shells from a mere 565 yards at minimum propellant charge, to a range of 4400 yards by having propellant-charge disks of powder added that by then were being manufactured as square disks with a hole in the middle, strung together, fitted into cartridges, and sewn together into bundles of various thickness. Its rate of fire was 40 rounds in the first two minutes, 100 rounds in the first 20 minutes, and at sustained fire 80 rounds per hour. These variations were caused by the stresses and strains on barrels and the rest of firing mechanisms, that were being imposed by different firing conditions.

The mortars were transported in mortar carts, jeeps, in island engagements in the Pacific by boat, and in difficult terrain by mule.

During the Allied attack on Sicily in the summer of 1943 - the first time the mortar had been used in war-time - 35,000 rounds of HE shells were fired in 38 days.

External links: