Sicily, July 1943.
A German tank is firing from a hillside in the dark, and two companies of American infantry cannot move.
No artillery has registered.
No air support is coming.
Then four mortar tubes open fire from a few hundred yards behind the line.
The shells make no sound in flight.
There is no whistle.
The last round drops directly through the open turret hatch.
The weapon that fired it was designed to deliver poison gas.
This is the story of the 4.2 2 in chemical mortar, a weapon built exclusively to hurl mustard gas and fosgene that never fired a single toxic round in combat.
Instead, it carried 8 lb of high explosive per shell.
The standard 105 mm howitzer carried 4.8.
A mortar weighing 330 lb outpunched a gun weighing 2 tons.
And every infantry commander in the American army had been told it was available, and almost all of them said no.
But the ones who saw it fire never refused it again.
To understand why the 4.2 existed, you have to understand a problem that had nothing to do with high explosive and a branch of the army that was fighting for its life.
After the First World War, the Chemical Warfare Service existed for exactly one purpose, preparing to deliver poison gas on the next battlefield.
Its primary tool was the 4-in Stokes Mortar, a British design that could lob chemical shells roughly 1100 yd.
The trouble was range.
1100 yd put chemical troops close enough to choke on their own clouds if the wind shifted.
The army wanted double that distance and in 1924 it gave Captain Lewis McBride at Edward Arsenal, Maryland a deceptively simple order.
Make it reach farther.
But by the time McBride’s team produced a weapon that worked, the institution that built it was nearly dead.
Through the 1920s and30s, the army tried repeatedly to abolish the chemical warfare service altogether.
In 1935, the War Department stopped all production of the 4.2 in mortar for a full year before Pearl Harbor.
The smaller 81 mm mortar replaced it as the authorized weapon for chemical battalions.
Chemical troops were never permitted to participate in peaceime field maneuvers.
They had a weapon no one had seen perform and a mission, poison gas, that the president of the United States had publicly sworn never to initiate.
Other branches circled, “Give the gas job to artillery.
Give it to the engineers.
Let the chemical warfare service disappear.” Then Major General William N.
Porter became chief of the chemical warfare service on May 31st, 1941.
And he understood something that his predecessors had not.
The service would die unless it proved its value with conventional ammunition.
In April of 1942, Porter formally requested permission to fire high explosive shells from the 4.2.
The Chemical Warfare Service had actually tested H rounds as far back as 1934, and McBride himself had developed one just before the war, but ground force commanders wanted nothing to do with it.
In their minds, the chemical warfare service meant gas and gas masks.
And in the words of the official army history, smelly clothing.
The field artillery board recommended the mortar be used only in theaters where the 105 mm howitzer was unavailable.
And since the howitzer went everywhere, that recommendation was a death sentence.
Porter played his final card in February 1943, a personal meeting with Army Chief of Staff George C.
Marshall.
His argument was arithmetic.
The 4.2 two could not match the howitzer’s 12,000yd range, but at comparable distances, its higher rate of fire delivered a payload on target rate 4 1/2 times greater.
The mortar weighed 305 lb.
The howitzer weighed more than 2 tons.
A howitzer battery of 12 guns required 12 officers and 325 enlisted men.
A mortar company with 12 tubes needed eight officers and 143 men, less than half the crew.
and the mortar’s lower velocity shells could be built with thinner walls, which meant a higher proportion of explosive filler inside each round.
The numbers were unanswerable.
On March 19th, 1943, the War Department authorized high explosive ammunition for the 4.2 and directed that field manuals be revised to train infantry commanders in its use.
The weapon that nobody wanted had 4 months to prove itself before the invasion of Sicily.
What McBride’s team had built in the 1920s was unlike any mortar in any army’s infantry.
And the reason started with a decision that broke every rule of mortar design.
Mortars are smooth boore weapons.
They have been since their invention.
A smooth boore tube is cheap to manufacture, easy to maintain, and fires thin stabilized shells that tumble predictably toward the target.
McBride ignored all of that.
He rifled the barrel.
The logic was sound.
fins had failed.
The propellant blast shattered them on launch, producing short and erratic flights.
Rifling would spinstabilize the shell instead, and spin stabilization meant accuracy and range.
But rifling a mortar barrel created problems that consumed years of engineering.
The machining process enlarged the bore from 4 in to 4.2 in, which gave the weapon its name.
Liquid chemical fillings mustard agent fosgene surged inside spinning shells and unbalanced them in flight.
Engineers solved this by fastening veins inside each shell to swirl the liquid in sync with the rotation.
Old fuses designed for tumbling Stokes shells armed themselves from centrifugal force and detonated at the muzzle.
Entirely new fuses had to be invented.
And then there was the problem of sealing the bore in a rifled artillery piece.
A brass driving band around the shell engages the grooves, but a mortar shell is dropped down the muzzle, and a conventional driving band would jam it halfway down.
McBride’s solution was the rotating disc.
Two round plates, one brass and one steel, stacked at the base of each shell.
When the propellant charge detonated, gas pressure rammed the steel plate against the softer brass one, forcing the brass edge outward into the rifling grooves.
The brass sealed the bore caught the rifling and spun the shell out of the tube.
Then the disc fell away.
It was a disposable objurating band rebuilt and discarded with every single round.
An engineer’s obsession made metal, a component that existed for a fraction of a second, and without which the entire weapon was a smooth pipe.
The complete mortar weighed 330 lb in three pieces.
a 40-in rifled barrel at 105 pounds, a hydraulic monopod standard at 53 pounds, and a forged steel base plate at 175 lb.
A fourman crew could drop 20 rounds per minute in short bursts, five per minute sustained.
Maximum range reached 4,400 yd with the improved propellant charges that arrived in December 1943.
But the detail that mattered most in combat was one no specification sheet captured.
The 4.2’s two’s low velocity spinstabilized shells traveled below the speed of sound.
They made no whistle in flight, no shriek, no warning.
Troops on the receiving end heard nothing until detonation.
8 lb of TNT arriving in absolute silence.
German soldiers in Sicily had no name for the weapon at first.
They only knew that buildings were collapsing around them and nothing had screamed overhead.
Some believed they were being hit by an automatic cannon because of the rate of fire.
Others called it the grass cutter because the shells detonated and fragmented just inches above ground level.
The invasion of Sicily was the 4.2’s trial by fire.
Four chemical mortar battalions, the 2nd, 3rd, 83rd, and 84th, went ashore beginning July 10th, 1943.
Lieutenant Colonel Robert W.
Brakes, commanding the second chemical mortar battalion, later said there was no book and no experience.
The weapon had never been used in combat.
Nobody knew how well it would perform.
His men had fired no more than 30 live H rounds per gun in training.
During earlier exercises, soldiers from other units had made braaying noises and cracked jokes about jackasses pulling carts at the chemical mortar crews hauling their equipment on foot.
Nobody was laughing now.
They learned fast.
At Grameell on the night of July 13th, a German tank was firing repeatedly into a company’s position with the 179th Infantry.
Lieutenant Dave Goodell and Captain Kyper crawled out between the lines with a radio.
Kyper got under a map with a flashlight to calculate coordinates.
They called in adjustments.
One of the last four rounds went directly down the open turret of the German tank, killing the crew.
Goodell later said the only reason it worked was the gun crew’s speed.
In pitch dark, they made precise small-cale adjustments and pulled the correct powder charges in under five minutes.
At dawn, 30 tanks and 500 German infantry hit the 179th.
Divisional artillery had displaced during the night and could not register.
A company’s mortars just a few hundred yards behind the line opened fire within minutes.
30 to 40 rounds per minute fell among the German infantry, forcing them to ground.
Without infantry support, the tanks became vulnerable to bazookas.
The attack stalled.
An officer present later wrote that without the 4.2s, the lead battalion of the 179th would have been overrun.
Meanwhile, the 83rd Chemical Mortar Battalion was earning the nickname Artillery of the Rangers supporting Colonel William Darby’s forces at Jila, where General Patton himself appeared behind a forward observer during a tank counterattack and barked his encouragement to keep firing.
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Now the real transformation came at San Frella Ridge in early August.
The assault was supposed to last one day.
It lasted 5.
Artillery had not registered and all fire support fell to three companies of the second chemical mortar battalion.
Germans located the mortar positions and hit them directly.
In one platoon, four of six guns were destroyed.
Then two battalions of the 15th infantry became pinned on the slopes, unable to advance or withdraw.
The commander of the 15th called Brakes to his command post.
Brakes told him he could start a smoke screen, but the mortars were firing from known positions and he did not know how long the company would survive.
The infantry colonel replied that they were either going to lose one mortar company or two infantry battalions.
Captain Lel Thompson volunteered his deco company.
Crews stayed in their holes with shells prepared, raced to the guns to fire, then dove back to cover.
The men called it Russian roulette.
The smoke screen held for hours under concentrated counter fire until full dark when the 15th infantry crawled to safety.
General Lucian Truscott commanding the third division issued a formal commendation.
The third division never questioned what a 4.2 mortar was for again.
Within 6 months of Sicily, General Mark Clark made it fifth army policy that no division would be committed to combat without a chemical mortar battalion attached.
When Patton’s third army became operational in the summer of 1944, his first standing order said the same.
In 38 days on Sicily, the four battalions had fired approximately 35,000 rounds.
By war’s end, 25 chemical mortar battalions had expended roughly 4 million rounds across every theater.
The 4.2 was not without honest limitations, and the most fundamental was weight.
330 lb assembled with the base plate alone at 175 made the weapon far too heavy for true man portable use across rough terrain.
One account describes dragging a mortar and 120 shells on carts for 12 m along a narrow mountain trail across a 2,000 ft ridge through swamps and over three rivers only to arrive too late.
Carl Pollson, a squad leader in the second chemical mortar battalion, remembered training marches of 17 mi in a single day, after which half his squad reported to sick call.
Range never satisfied the infantry either.
Even the improved 4,400y maximum was less than half the howitzer’s reach, and troops in the field demanded 5,000 yd or more.
Parts breakage was chronic.
elevating screws bent, base plates cracked, barrel housings split under the stress of propellant charges the original design was never built for.
Forward observers suffered appalling casualties.
The 87th Battalion’s journal recorded that scarcely a day passed without one or all of the observer party being wounded or killed, but those limitations were the price of the weapon’s essential nature.
The base plate weighed 175 lb because it had to absorb the recoil energy of a shell carrying more explosive than light artillery.
The range was shorter because the lower velocity that limited distance was the same low velocity that made the shells silent in flight.
Every weakness pointed back to the same truth.
This was a weapon that traded range for lethality and mobility for devastation at close quarters.
The infantry did not love it despite its flaws.
They loved it because of what its flaws made possible.
The 4.2’s war did not end in 1945, and its reach kept expanding in ways no one predicted.
When replacement troops arrived at the 91st Chemical Mortar Battalion, many had imagined themselves working in laboratories behind Bunson burners and assorted glassware.
When shown the mortars three simple parts, one man asked what made it shoot since the thing had no breach.
Another muttered that the weapon would require a man to get too close.
They were not wrong about the close part.
On D-Day, June 6th, 1944, the 81st Chemical Mortar Battalion landed on Omaha Beach with Vcore.
Its commander, Lieutenant Colonel Thomas James, seriously wounded before reaching shore.
Captain Thomas Moundres of a company was killed before setting foot on sand.
The 87th went ashore at Utah Beach during the first hour and began firing over the bluffs immediately.
For nearly 6 hours, the 4.2 2-in mortars were the only ground weapons capable of delivering heavy fire support at Utah.
By July 1st, the 87th had fired more than 31,000 rounds in 25 days of continuous combat.
In the Pacific, the weapon found an entirely unexpected second life at sea mounted on landing craft infantry to create mortar gunboats carrying three tubes each.
At Okinawa on April 1st, 1945, 42 of these gunboats carrying 126 mortars saturated a strip of beach 5 1/2 m wide with more than 28,000 rounds in under an hour.
Vice Admiral Thomas Concincaid concluded that the mortifier was more effective for beach neutralization than strafing from his carrier aircraft.
On land at Buganville, Company A of the 82nd Chemical Mortar Battalion expended 20,250 rounds in three weeks during the Japanese counterattack at Empress Augusta Bay.
Captured Japanese documents ordered their own artillery to concentrate fire on mortar units whenever possible.
The highest compliment an enemy can pay.
The second chemical mortar battalion, the same unit that fired the first shots in anger at Sicily, was reactivated and deployed to Korea in 1950, where it served 1,7 consecutive days in action without relief, supporting six American divisions, eight Korean divisions, and the 27th British Commonwealth Brigade.
On January 22nd, 1953, the battalion was redesated as the 461st Infantry Battalion, Heavy Mortar.
The gas weapon had become officially and permanently an infantryman’s weapon.
The M30 mortar succeeded the M2 in 1951, retaining the 4.2 in rifled barrel concept but nearly doubling the weight for extended range.
The M30 served through Vietnam where Marines mounted it on a howitzer carriage and called it the Howar.
The M2 was formally retired in 1974.
Surviving examples stand at the Chemical Core Museum at Fort Leonardwood, Missouri, and at the Pennsylvania Military Museum.
Quiet steel tubes behind velvet ropes, stripped of propellant and purpose, waiting for someone to explain what they once did.
No whistle, no warning.
The shells that arrived in silence at Gishelle carried 8 lb of high explosive and the entire future of a branch of the army that nobody wanted.
And now you know why the silence was the point.
The mortar that was built to deliver poison gas delivered something the infantry needed more.
Not chemicals, not range.
