October 1942, Lalamagne, the 66th Mortar Company, Royal Engineers, has just received its new weapons. These mortars look nothing like the lightweight tubes infantry carry. They weigh over 1,300 lb. They require vehicle transport. They fire bombs twice as heavy as anything a battalion mortar can manage. And tonight, they are about to do something no British unit has ever done before.
According to contemporary accounts, this single company will have expended the 4.2 2-in high explosive ammunition available in the North African theater during that action. An extraordinary expenditure that speaks to how desperately commanders wanted this weapon’s fire. The mortar that accomplished this feat was designed to deliver poison gas.
It never gassed anyone. Instead, it became one of the most devastating fire support weapons the British army possessed. A weapon that could sustain grinding bombardments for hours, delivering 20 lb bombs at short burst rates that artillery officers found remarkable for a heavy mortar. This is the story of the Ordinance ML 4.
2 in mortar, the chemical weapon that became a hero. The problem facing British planners in 1941 was simple to state and difficult to solve. Infantry battalions had the 3-in mortar, a fine weapon that could lob a 10-lb bomb roughly 2,800 yd. Divisional artillery had 25 pounders reaching out beyond 11,000 yd. But between these two systems lay a gap, a range band where infantry needed fire support heavier than their battalion weapons could provide, yet closer and faster than divisional guns could deliver.
German forces exploited this gap ruthlessly. Their 81 mm Granite Vera 34 fired at 15 to 25 rounds per minute, saturating British positions with 7.7 lb bombs before artillery observers could even call for counter fire. Worse still, the Germans had developed something that terrified Allied soldiers across every theater, the Naval Verer.
British troops called it the moaning mini. Because of the distinctive wailing sound its rockets made in flight, a single Naval Wer battery could deliver 36 rockets in 10 seconds. Over 2500 lb of high explosive arriving almost simultaneously. The psychological effect was devastating. Men who could endure hours of conventional shelling broke under Neble Verer attacks.
The screaming approach, the massed explosions, the sheer violence of the salvo. It overwhelmed even veteran formations. What the British needed was not another weapon to match the Nebleworf’s shock effect. They needed something that could deliver sustained, grinding, relentless fire support. Something that could keep German heads down for minutes and hours rather than seconds.
Something that could turn the defender positions into a continuous hell of explosions. The solution came from an unexpected source. The armament’s research and development establishment had been working on a chemical weapons delivery system, a heavy mortar designed to saturate enemy positions with mustard gas.
According to design documents cited in Pew’s fighting vehicles and weapons of the modern British army, ARDE engineers created a smooth bore mortar of 4.2 in caliber, firing thin stabilized bombs through a barrel 68 in long. The weapon they produced was massive by mortar standards. The MK2 barrel alone weighed 92 lb. The mounting added another 112.
The mobile base plate and genius trailer design, whose wheels could be unlocked and raised for firing, weighed 602 lb, total system weight approached, 1320 lb, more than 10 times heavier than the 3-in mortar it was meant to complement. This weight bought capability. The 4.2 2-in mortar fired a 20 lb high explosive bomb at 730 ft pers reaching out to 4100 yd with the standard charge.
According to Chamberlain and Gander’s mortars and rockets, the weapon could sustain 10 rounds per minute continuously, increase to 15 rounds per minute for 3minut bursts, and peak at 20 rounds per minute for 1 minute intense fire missions. The mathematics made artillery officers take notice. At 15 rounds per minute, the 4.
2 2-in mortar was putting 300 lb of ordinance downrange every 60 seconds. A four mortar platoon could deliver 1,200 lb per minute. A 16 mortar company could sustain nearly 5,000 lb of high explosive per minute onto a target area. All arriving at near vertical angles that maximized blast effect against troops in trenches and foxholes.
The mobile base plate deserves particular attention because it represented genuine engineering innovation. Unlike conventional mortarbased plates that simply absorbed recoil into the ground, the British design incorporated an integrated trailer with suspension arms and wheels that could be unlocked and swung up for firing.
This dramatically improved mobility and reduced the time needed to bring the weapon into action compared to separated components. A Lloyd carrier towed the complete assembly, and crews could be firing within minutes of arrival. The weapon offered elevation from 45 to 80° and 10° of traverse, allowing rapid adjustment without repositioning the base plate.
Ammunition came in multiple configurations. The standard high explosive bomb weighed 20 lb. Smoke bombs ran slightly heavier at 22 lb. During the war, British industry produced both streamlined and cylindrical bomb bodies. Production pressures in 1941 and 42 forced manufacturers to use cast bomb bodies rather than the intended forge types, reducing range and consistency.
This explains the variable range figures across sources, anywhere from 3,300 to 4,400 yd depending on bomb type and charge. Two propellant charges were available, allowing crews to adjust trajectory for different tactical situations. Charge 2 provided maximum range. Charge one gave a higher, slower trajectory ideal for engaging targets in defilade or behind obstacles where near vertical impact was essential.
Royal Ordinance factories began production in late 1941. By wars end, approximately 3,800 had been built. The mortar entered service with Royal Engineer Chemical Warfare Companies, complete with Mark1 chemical bombs filled with mustard gas designated HS or HT fillings. These units trained to deliver poison gas attacks. They never did.
Gas warfare remained a threat that never materialized. By mid 1943, the War Office concluded that chemical attacks were unlikely and disbanded the RE chemical warfare companies as an emergency expedient. The mortars were too valuable to waste. They passed to infantry divisions assigned to machine gun battalions as heavy mortar companies.
Each division received 16 mortars organized into four platoon of four providing organic heavy fire support that infantry commanders could call upon directly without waiting for divisional artillery allocation. The transition was not smooth. New Zealand’s official war history delivers a damning verdict on the war office’s handling of the weapon.
The historians wrote that the war office had been strangely remiss about the way it had these weapons produced and issued without serious thought about who should use them or how they should be used. Infantry battalions chronically short of manpower and especially officers lacked the training and communications equipment to employ the mortars effectively.
Fire control procedures that artillery men learned as basics were unknown to infantry officers suddenly responsible for heavy indirect fire weapons. The New Zealand solution proved characteristic of Commonwealth pragmatism. The seventh anti-tank regiment formed 39th mortar battery in April 1944, putting the heavy mortars in the hands of artillery men who understood fire control.
Second left tenant RR Menendez prepared the first proper range table for the weapon, something the War Office had apparently never done. These gunners would fight the mortars as artillery, not as oversized infantry weapons. Similar improvisations occurred throughout the British army. At Casino, S troop of 307th Battery, 99th Light Anti-aircraft Regiment, manned 4.2 in mortars.
Anti-aircraft gunners repurposed because heavy mortar crews were unavailable. In Borneo, decades later, air defense battery personnel would man the same weapon. The 4.2 in mortar became the weapon that formations kept reaching for when they needed heavy fire support fast. Elamine proved the concept. The 66th Mortar Company supported the Australian 24th Infantry Brigade’s advance, providing intense fire on the brigade’s exposed right flank.
The crews fired continuously, burning through ammunition at rates that shocked supply officers. Contemporary accounts credit the company with using up the 4.2 2in H stocks available in the North African theater during that action. An extraordinary expenditure. This was not poor logistics. This was a weapon system proving its worth so dramatically that commanders kept demanding more fire.
Now, if you are finding this interesting, a like on this video genuinely helps more than you would think. The algorithm notices. Now, back to the mortars combat record. Italy provided continuous validation at Anzio. Imperial War Museum photographs show First Infantry Brigade Support Group firing in support of the fifth Northamptonshire Regiment during the May 1944 breakout.
The weapon’s high angle trajectory made it lethal against fortified mountain positions, delivering bombs at near vertical descent into German foxholes and trenches. A bomb falling straight down maximizes blast effect against dugin troops. The 4.2 in mortars plunging fire turned German field fortifications into death traps. The fourth battle of Casino in May 1944 saw massed 4.
2 inch fire integrated into core level fire plans. Operation Diadem brought every available gun and mortar to bear on the German Gustavline defenses. The mortars fired alongside medium and heavy artillery and coordinated programs that left German defenders unable to move, unable to reinforce, unable to do anything except endure the continuous reign of explosions.
Normandy and northwest Europe continued the pattern. During Operation Jupiter in July 1944, the recapture of Hill 112, 4.2 in mortars were incorporated into Army Group Royal Artillery fire plans for counterbatter and countermortar tasks. The second Kensingtons of the 49th West Riding Division operated their mortars from the beaches through to Arnham.
An Imperial War Museum sound recording captures British 4.2 2-in mortars firing near Boxtell, Netherlands on October 23rd, 1944. The weapon proved particularly effective in the close country of Normandy’s Bokeage. German defenders used the thick hedge to create interlocking defensive positions that artillery struggled to neutralize.
The high angle mortifier dropped bombs directly into these positions, bypassing the natural cover that protected against flat trajectory weapons. Infantry advancing through the barage learned to call for 4.2 in support when they identified strong points. Trusting the near vertical bomb descent to reach defenders that artillery could not touch, countermortar work became an important secondary mission.
German mortar teams caused constant casualties among advancing British units. The 4.2 in mortar could respond faster than divisional artillery, saturating suspected German mortar positions within minutes of being called. Sound ranging equipment helped locate German weapons by the distinctive thump of their firing.
Once located, a concentration of 20 lb bombs often silenced them permanently. One veteran claimed that a trained crew could put 23 bombs in the air before the first one impacted. At maximum charge and high elevation, the bomb’s flight time exceeded 1 minute. A crew loading at 20 plus rounds per minute could theoretically achieve this effect.
A devastating rain of 20 lb bombs arriving almost simultaneously. Whether precisely accurate or not, the anecdote speaks to the weapon’s sustained fire capability, its ability to keep bombs falling on target for as long as ammunition lasted. Korea brought the weapons finest hour. At the battle of the Imjin River in April 1951, sea troop of the 170th independent mortar battery, Royal Artillery fought alongside the first battalion Glostershare Regiment.
The Glousters made their legendary last stand against overwhelming Chinese forces and the Mortimemen fought beside them. The battle unfolded over 3 days of desperate fighting. Chinese forces attacked in overwhelming numbers, wave after wave of infantry pressing against British positions. The mortar crews kept firing, adjusting their aim as the perimeter shrank, dropping bombs ever closer to their own positions as the Chinese advanced.
When ammunition ran low, they called for resupply. When resupply could not reach them, they rationed their remaining rounds for maximum effect. Sea troop received the United States Presidential Unit Citation, an exceptionally rare honor for a British unit for exceptionally outstanding performance of duty and extraordinary heroism near Smarie.
The citation recognized mortar crews who kept firing in support of surrounded infantry who refused to abandon their weapons even as Chinese forces closed around their positions. The 4.2 in mortar had proved itself in the deserts of Africa, the mountains of Italy, the hedge of Normandy. At the Immun, it earned recognition from an Allied nation for extraordinary valor.
Comparing the British 4.2 in to its counterparts reveals the engineering philosophy behind the design. The AmericanM2 4.2 2-in mortar shared the same caliber, but little else. The Americans rifled their barrel, creating spinstabilized shells that achieved slightly greater accuracy and packed 8 lb of explosive, roughly comparable in blast effect to medium artillery shells.
The American weapon weighed just 333 lb, a fraction of the British systems 1300. This weight difference reflected different tactical concepts. American chemical mortar battalions deployed 48 mortars each using lightweight as a force multiplier. British divisions had 16 mortars per heavy mortar company. Using the mobile base plate sophistication to improve mobility and reduce implantment time.
The American approach scattered many light weapons across the battlefield. The British concentrated fewer heavy weapons for maximum effect per round against the German 8 cm granite verifer 34, the standard Vermach infantry mortar. The 4.2 2 in delivered decisive overmatch. The German weapon fired its 7.
7lb bomb at 15 to 25 rounds per minute. The British mortar fired its 20 lb bomb at 10 to 15 rounds per minute sustained. In weight of ordinance per minute, the 4.2 in delivered 200 to 300 lb versus the German weapons 115 to 193 lb. The Nabalwer remained a different beast entirely. The 15 cm Nabblewer 41 achieved 6,900 m range, nearly double the 4.2 2 in mortars reach.
Counterb fire against neeblewer positions was primarily accomplished by conventional artillery. Directed by sound ranging, flash spotting, and countermortar radar, the 4.2 in could theoretically engage Nebleworfer positions brought close to the front, but this was not its designed role.
Where the Nebbleworfer delivered terrifying but brief salvos, the 4.2 in delivered grinding, sustained, relentless bombardment that kept defenders pinned for hours. The 4.2 2-in mortar served beyond the Second World War, beyond Korea, into conflicts its designers never imagined. British forces deployed the weapon to Kuwait in 1961. During the crisis following Iraqi threats to the newly independent Emirate, air defense battery personnel manned the mortars during the Borneo confrontation in 1965.
The weapon finally retired from British service around 1966. A quarter century after its introduction, other nations extended its service life further. Australia, Canada, India, New Zealand, Malaysia, Nepal, Greece, Turkey, Ethiopia, and Sri Lanka all operated the weapon. In one particularly improvised application, reserve stocks of 4.
2in mortar bombs were dropped from Sri Lanka Air Force helicopters as improvised munitions during the early stages of the Sri Lankan Civil War. Mortar bombs designed to fall down a tube, instead dropped from aircraft decades after their manufacturer, still deadly enough to be worth the improvisation. The weapon’s legacy lies not in a catchy nickname, but in what it represented, the British answer to the problem of heavy fire support.
Between battalion mortars and divisional artillery, where the moaning Mini screamed and terrified and fell silent, the 4.2 in mortar thumped and crashed and kept on firing. It was not glamorous. It was not terrifying. It was relentless, methodical, crushing, and effective. The institutional journey of this weapon tells its own story.
Born as a Royal Engineer chemical weapon, transferred to infantry machine gun battalions, finally adopted by the Royal Artillery, the 4.2 in mortar moved between services more than most weapons of its era. This unusual institutional path meant no single regiment strongly claimed it. No deep tradition grew around it. No songs were sung about it.
Yet every formation that used it demanded more of them, more ammunition, more missions, more fire support from the heavy tubes that could reach where battalion mortars could not. and respond faster than divisional artillery. 3,800 were built. They served from Alamagne to Korea to Borneo across three continents and three decades, proving that British engineers understood something fundamental about sustained fire support.
Sometimes victory goes not to the weapon that screams the loudest, but to the one that keeps firing longest. The 4.2 in mortar kept firing until there was nothing left to shoot, and then its crews asked for more ammunition and kept firing again. That is not glamour. That is not terror. That is effectiveness, pure and sustained. That is what British engineering built.
That is what British soldiers carried into battle. That is the weapon whose crews expended a theat’s worth of ammunition in a single engagement because commanders kept demanding more fire. The chemical weapon that never delivered.
