Chemical mortar battalion The United States chemical mortar battalions were army units attached to U . S . Infantry division s 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 " . Chemical mortar battalions . Originally , chemical mortar battalions consisted of four mortar companies and a HQ company . In 1943 , this " square " organization was modified to three mortar companies for a better fit with the three rifle regiments of the " triangular " infantry divisions . After the 1943 reorganization , 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 : 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 . The numbers of the battalions . 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 . The 2nd Chemical Mortar Battalion was the last of the chemical mortar battalions ; and the only one to see combat after World War II . It was reactivated in 1949 and saw 1 , 008 days of combat during the Korean War . In January 1953 , its combat personnel were transferred to the 461st Infantry Battalion ( Heavy Mortar . ) 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 shell s . Chemical shells were on stand - by during World War II , to be used in retaliation should the enemy employ chemical weapon s first . These same mortar s , 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 , pillbox es and even the powerful German 88 mm gun s . Other advantages chemical mortars offered were their maneuverability , easy assembly , disassembly and reassembly from one location to another . The mortars were able to fire high - explosive shells from concealed positions , such as natural escarpments on hillsides , or from woods . The rifled barrel gave the mortar remarkable accuracy ; fire was often called on targets within fifty yards of friendly positions . The low - velocity shell was totally silent in transit and gave no warning of the huge thump of the explosion , which tended to create panic among enemy forces who were subjected to their firepower . The mortar was called the " grass - cutter " by German troops because its HE shell exploded and fragmented just a few inches above ground level . The mortars often fired white phosphorus ( WP ) shells to block enemy observation with smoke ; WP also caused casualties and fires , being especially effective against dug - in troops because the burning WP particles arced upward and fell directly down into foxholes . The development and capabilities of the chemical mortar . The 4 . 2 in ( 107 mm ) chemical mortar was developed from the British World War I 4 inch Stokes mortar . A " Stokes " mortar could fire twenty shells a minute and had a range of 1 , 100 yards ( 1 , 006 m ) and in this way was capable of overwhelming enemy trenches . The 4 . 2 in ( 107 mm ) mortar , which by then had a rifled barrel installed and was firing shells with fins attached , had a range of 2 , 300 yards by 1924 . After modifying the bore , improving the two - legged support and the recoil mechanism , and producing barrels made of seamless nickel steel , the M1A1 model was capable of sending shells 2 , 400 yards ( 2 , 195 m ) during the 1930s . By 1942 , after authorization had been sought and granted to use high explosive shells , the new M2 model was being built with stronger barrels . History . In 1935 , the 2nd Chemical Mortar Battalion was established at Edgewood Arsenal Maryland with the chemical mortar as its primary weapon . At the onset of World War II , there were a few other mortar battalions and companies , including one that was lost on Bataan in the Philippines . In 1942 , General George Marshall ordered the formation of five additional chemical mortar battalions equipped with the mortar . ( These were the 3rd , and the 81st through 84th . ) Later , the mortar was developed to be capable of instantly firing shells from a mere 565 yards ( 517 m ) at minimum propellant charge , to a range of 4 , 400 yards ( 4 , 023 m ) 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 cartridge s 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 thereafter a sustained rate of 80 rounds per hour . These variations were caused by the stresses and strains on the barrels and the rest of firing mechanisms that were being imposed by different firing conditions . The mortars were transported in 3 / 4 ton trucks or on hand carts , in island engagements in the Pacific by boat , and in difficult terrain by mule . During the Allied invasion of Sicily in the summer of 1943 - the first time the mortar had been used in war - time - 35 , 000 rounds were fired in 38 days , of which more than 90 % were HE .