Mills Bomb 'hand grenade'



With no anticipation of a prolonged siege-type war, the British Expeditionary Force (BEF) moved to France in August 1914 without any equipment that had been purpose-made for the trench warfare that was shortly to engulf it. Amongst the equipment it did have available was what has been graphically described as 'a meagre supply of unsuitable hand grenades'. In fact, in November 1914, the BEF was only supplied with 70 hand grenades per week from the UK arsenals.

Within weeks of their arrival on the Western Front, the remnants of the BEF were fighting under static trench warfare conditions as the shattered armies dug in. Pre-war, the British military planners had predicted that the effective fighting range, in an European War would be around 500 yards, with accurate and rapid rifle-fire, backed by mobile field artillery, being the prime requirement for success. The British generals had plans for dashing cavalry charges to back large scale infantry assaults in a war of rapid movement over open ground. In effect the trenches reduced the battlefield to a No man's land of an average of 250 yards as the minimum distance separating the British and German lines, but it was often much less: 7 yards was reported at Zonnebek in Flanders. And the artillery became much more than a support arm. Moreover, the British troops found that the Small Magazine Lee-Enfield (SMLE) rifle, with sword bayonet attached, was difficult to wield in the crowded trench, and particularly so in the man-to-man fighting that often developed in enemy assaults on the trenches and vice-versa.

Quickly the British learned that the Germans had a good supply (around 70,000) of their ball grenades and found that they used them with some skill. (The infamous German 14-inch long stick 'Potato Masher' grenade only became operational in 1915).

As already stated, the only operational British grenade in 1914 - the 1908 No. 1 Mark I Percussion Stick Grenade - was strictly limited in supply. It was based on a Japanese medieval mace-like design that, once armed, immediately exploded when the grenade head hit an object; any object. The 22-inch overall length of the throwing handle plus the grenade head made it awkward to manipulate. The head also carried canvas streamers that served to steady the grenade in flight, but could easily snag when the grenade was thrown. Once armed with the detonator, it became particularly dangerous to use in the limited confines of the trenches. And there were many accidents, both in and out of the trenches. Many commanders became very wary of issuing them to the untrained infantryman and some of the instructors, because of the safety problem, instructed their men to reverse the No. 1 and throw it like a dart, which totally negated the advantage of the long throwing handle.

But, along with the rifle and trench mortar (also in very short supply), the grenade quickly become the principal means for the trench bound infantry battalions to attack and repel the enemy; sources of hand grenades had to be found, urgently.

The options were few and immediate prospects not very bright.

The race to production

An immense effort was begun to produce a standard hand-grenade for the British Army. Inventors were encouraged to submit designs and what at first was a trickle of contenders became a flood. In a period of a year, 12 different designs were under evaluation or in limited prototype production.

Whilst this process of design and evaluation was being established, recourse was made to an existing British manufacturer - the Cotton Powder Company - supplier of percussion hand grenades to the Mexican Government. Similar in both form and action to the existing British No.1 Percussion Grenade, it became the British No.2 Percussion Grenade, but was also known as the Mexican Pattern or the Hale's (after the British designer). Unfortunately, it too suffered from the tendency for accidental detonation, and the disadvantages of a long throwing handle; the handle was subsequently shortened. Production of the No. 2 Percussion Grenade for the British Army began in early 1915. By the end of 1915, around 2,000 per week were being produced. Although this was far from the anticipated requirements, most of the BEF had yet to master the skill of bombing with hand grenades, and some commanders still had doubts about their utility. There were also problems about finding suitably reliable detonators and the industrial capacity to manufacture them in sufficiently large numbers.The evaluation of the new hand grenade designs was entrusted to Colonel Louis Jackson who was the Assistant Director of Fortification and Works in the British Army. Other departments and committees were peripherally involved, but most of the initiative came from Jackson's department. He was very active and had a good eye for a good idea.

By the end of 1915, the 12 different designs had been submitted to the various evaluation committees and a few had gone into limited production as a stopgap measure until production of the definitive hand grenade could begin. Two of the interim designs were the famous improvised 'Jam Tin' and 'Hairbrush' designs by Jackson, (See the article British ad hoc weaponry of the Western Front in the Great War for further details). However, none used the discredited percussion fuse technology and the time-fuse/detonator became the British standard.

The entry of the prime contender

In Belgium, in early1914, two inventors produced a radically new design for a hand grenade. One was Albert Dewandre who worked for a munitions company - the Compagnie Belge de Munitions Militaire - and the other Captain Leon Roland who was an officer in the Belgian Army. The design of their hand grenade did away with the need for a fuse that had to be lit by hand - it had an automatic fuse igniter and a detonator all incorporated in the body of the grenade. Unfortunately, Captain Roland was captured as a Prisoner Of War by the Germans whilst on active service in November 1914. Monsieur Dewandre was left with a grenade with teething problems and no one to assist him to sort them out.

By chance, in December 1914, Dewandre met a British designer and manufacturer by the name William Mills who had had a lot experience in foundry work. A rather desperate Dewandre discussed the development of the new style hand grenade and asked for Mills' technical advice. Mills was much impressed by the new concept and suggested they work together to produce a version that could be mass-produced without too much refined machining work. In the process of this work Mills developed ideas different from Dewandre and felt he had created the essential elements of a unique design from a good concept.

In January 1914, the two co-inventors took their prototype to the newly formed British Inventions Branch of the Royal Artillery who were suitably impressed. They quickly gave permission for further development and trials.

Mills submitted patent claims for the parts he has designed, or redesigned, and these were granted by the Autumn of 1915; others followed. Other parts of the grenade had been designed by other inventors and these parts were also patented. Meanwhile, the early field trials had been successful and the approval was given for the Mills grenade to go into large-scale production as the No. 5 Mills Mk I Hand Grenade (later widely called the Mills Bomb).

The specification of the Mills Hand Grenade

The No. 5 Mills Hand Grenade is perhaps simply described as barrel shaped and 1.5 pounds in weight. The cast iron casing was segmented into squares - rather like a pineapple - with two objectives. Firstly to provide a firm grip for the thrower, and secondly to assist fragmentation of the casing to provide shrapnel which, combined with the effect of the high explosive, would cause injury to the enemy. (Much later studies indicated the grooved casing did not enhance the fragmentation affect).

The grenade was composed of the following parts:It fitted neatly into the hand of the average soldier and inspired its delivery in what was a second-nature natural bowling action to the cricket loving BEF soldiers.

  • The hollow cast iron casing.
  • A sealed brass plug at the top for filling the grenade with the high explosive called Tonite - a preparation of gun cotton.
  • A knurled base plug for inserting the ignition device. In later grenades this pin was recessed and threaded to insert a rodded rifle grenade projection device.
  • A central aluminium housing that held the ignition device. This comprised of a spring tension firing pin, a percussion cap to arm the time delay fuse - 5 seconds was the norm - and the detonator that was located in an off set chamber.
  • A steel lever that held the spring of the ignition device under tension;
  • A safety pin that locked the arming lever in place until the pin was removed. When the pin was removed the lever was held in place by the thrower's hand. After the grenade was thrown, the lever flew off and set off the time fuse that had a predetermined delay, (say five seconds) then the detonator and, ultimately, the explosive. If the lever had not been released, the safety pin could be replaced and the grenade neutralised for use at a later date.

For safety reasons the ignition devices were stored separately from the main grenades in the 12 grenade transportation box and were inserted through the base plugholes in the Front Line.

After some initial fluctuations, the cost ex-factory settled at around six shillings per grenade.

The Mills Hand Grenade becomes operational

The Mark I version of the No. 5 Mills Hand Grenade become operational in early 1915. But there were problems in the production process and further changes had to be made that delayed large-scale production until mid-1915. By which time an order for 5 million of the Mills grenades had been placed by the British War Office. Frantic expansion of the production process over dozens of contractors rapidly boosted production: in October 1915, 300,000 units a week were delivered to the British Army; more than double what had been expected.

On the battlefield, there were some initial problems with defective grenade levers, strikers and fuses. Accidents occurred at the rate of one per 3,000 grenades thrown. Appropriate changes and adjustments were made and, allied with the growing expertise of the dedicated teams of Mills bombers on the Western Front, the casualty rate declined.

Training in use of the No. 5. Mills Grenade

Most field commanders realised the importance of proper training in grenade handling. Intensive practical training courses were held both in and out of the Front Line.The cricket-ball bowling action for the No. 5 Mills grenade became the standard with the aim of 22-yards - the length of a cricket pitch - being the desired optimum range.This allowed a high trajectory which facilitated dropping the Mills Bombs directly into a 4 -feet wide trench. For other targets, 30 yards was considered the norm. Of course, expert bombers were developed who could exceed these range limits considerably and with consistent accuracy.

Bombers were taught to count to three after releasing the hand lever, and before throwing the grenade. This was to avoid the recipient(s) taking avoidance action, or even throwing back the grenade.

Second generation Mills Hand Grenades

In 1916, the No. 23 Mills Mark II grenade was introduced which incorporated the required changes. It was reported by the BEF to be more reliable than the No. 5 Mills Mark I. But some of the highest ranks of the BEF, including General Sir Douglas Haig still held the grenade to be subordinate to 'accurate rifle-fire': sadly most of the expert 'Contemptible' riflemen were dead by then, or out of action.

This was followed in mid-1917 by another radical redesign by the British Trench Warfare Department, but without Mills' participation and approval; he thought the changes were unnecessary. In particular the hand lever and the firing mechanism were redesigned to make the firing mechanism virtually fool-proof and thus avoid the many accidents that were caused by dropping the grenade after the safety pin had been pulled. This model - the No. 23 Mills Mark III Hand Grenade - and a virtually similar grenade - the No. 36 - became the standard Mills Bombs for the rest of the war on the Western Front. And the BEF's 'Specialist Bomber Platoons' became some of the most expert and productive ground fighters of the Great War.

Rifle grenades

A further logical extension of the use of the hand grenade was to considerably increase its effective range by projecting it by a propellant from a device affixed to a standard infantry rifle. This had become an important development of the hand grenade and by the end of the war special rifle grenade throwers were in production.

By the process of fitting a steel rod of a suitable diameter to the base of a grenade, almost all of the early types could be fired from a standard rifle using a blank cartridge. The British No.5 Mills hand grenade was so used. Other devices such as a specially designed 'grenade cup' attachment were attached to the rifle for the same purpose.

In 1914, the BEF had no rifle grenades, whilst the Germans did. However, as already related, a British manufacturer was producing some for the Mexican Government and the British commandeered all future production.

Thus the first British candidate was the Hale No. 2 that used the rod technique; unfortunately this quickly wore out the rifle and if the rifle was used repeatedly, it could burst. A more sophisticated and expensive version - the Hale No. 3 - came into production in 1915.The first grenade that could be used both as a hand grenade and a rifle grenade was the No. 5 Mills Mark I. With the invention of the 'No. 1 Mills Mark I Grenade Cup its combination with the rodded No. 23 Mills Mark I Hand Grenade became highly practical with a range of 160 yards and was quickly adopted the standard for the BEF.In mid-1917 the rodded grenade was replaced by the non-rodded No 23 Mills Mark III allied with a device called a 'cup discharger' invented by a New Zealander Robert Burns. This arrangement not only gave two-and-a-half times the range; it was more accurate to aim. It also resolved the problem of over pressurising the rifle barrel and eliminated the accidents associated with this.


The BEF went to the Western Front in August 1914 with a small supply of rather dangerous-to-use hand grenades mainly intended for specialist use by the Royal Artillery and the Royal Engineers. By the Armistice the BEF and the American Expeditionary Force (AEF) had been supplied with over 30 million Mills' hand/rifle grenades which had been made as safe to handle as any such lethal object could be.

The hand and rifle grenade had become stock-in-trade to every soldier and was a highly effective tool of war in the hands of the specialist trench-bomber.

N.B.: Any reader requiring a more detailed account of hand grenades and other small arms used in trench warfare in the Great War is referred to the book written by Anthony Saunders, Weapons of the trench war 1914-1918. (1999, Paperback 2000). Published by Sutton Publishing. ISBN 0 7509 2505 1. The author found this reference extremely helpful in clarifying technical details of British hand grenade design and production.

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