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The Mills bomb hand grenade

When the empires of Europe clashed in 1914, military commanders struggled to adapt to the new weapons available on an industrial scale. Military technology was further developed, and new ways found to use it. In this blog post, we take a look at the No.5 Mark 1 Mills grenade, first British hand grenade ever to be issued on a large scale.

Development of the No.5 Mark 1

During the First World War, the War Department believed that the Belgian designed self-igniting hand grenade would be a valuable asset for British soldiers in the trenches. Patented in 1912 by Captain Leon Roland of the Belgian Army, the Compagnie Belge de Munitions (CBdM) was established in order to market the grenade to a British manufacturer.

The task was given to William Mills of Mills Co. An experienced engineer, he was given the task of redesigning the grenade, making it safer and more efficient than its Belgian counterpart.

After a few false starts, Mills in 1915 sent prototypes to the troops in France of his cast iron bodied, egg shaped grenade. Eventually this prototype became the No.5 Mark 1 and was the first British hand grenade ever to be issued on such a large scale.

Resembling a small pineapple due to its segmented outer form, these segments were originally designed to fragment. Due to the nature of explosives, however, they failed to do so, but instead provided a firm grip in the wet conditions of the trenches.

How was it used?

To detonate the grenade the safety pin had to be removed. Once the pin was pulled out, by use of the attached ring, the user would hold the lever down and prepare to throw. When thrown the lever would release. As the lever released the striker would drop onto a percussion cap, the blast from which lit the fuse. This burned for five seconds before it reached the detonator.

A good bomber would have to be able to throw a bomb to a distance of around 30.5 m (100 feet), thus protecting themselves from the blast. It was deemed that cricketers, especially those with a good bowling arm, made the most effective bombers.

The No.5 grenades were supplied to the infantry in wooden chests, each containing 12 grenades, with a tin of igniter sets. These complete detonator units each comprised the detonating charge, a 5-second fuse, and a cap chamber housing the initiating percussion cap, along with a base plug key.

Diagram of a No 5 Mills hand grenade

Instructional diagram showing the Mills Hand Grenade, Godstone Grenade School, Britain, 1917, taken from a loose-leaf notebook belonging to Lieutenant J.M.Y Trotter, No.2 Officer Cadet Battalion, relating to his training.

Arming a Mills bomb was straightforward, requiring only that the base plug be unscrewed, the detonator assembly inserted and the plug screwed back down. This was always done ahead of time and whilst in cover, but remained an inherently risky task. Private Clarrie Jarman, a scout bomber of the 7th Queen’s Regiment recalled: “There was a bang and screams and the stretcher bearers went at the double to some poor devils who had let their concentration wander.”

Personal recollections

Private J. Curdie, 6th Battalion, Highland Light Infantry/Royal Flying Corps

Private Curdie describes how to make improvised hand grenades out of jam tins (mp3, 2 MB). [download transcript (txt, 2 KB)].

Private Thomas Nash, Manchester Regiment

Private Thomas Nash gives a gruesome account of the effects of throwing a Mills bomb hand grenade at a German soldier (mp3, 3 MB) [download transcript (txt, 2 KB)] being under machine gun and artillery fire, and going ‘over the top’ with bayonets fixed. He enlisted in 1916 and served on the Western Front.

What effect did they have on trench warfare?

These grenades were an essential part of trench warfare, in particular during raids. Interestingly, notes from a bombing course that took place at the School of Arms in Hythe in January 1920, still taught the tactics of bombing a trench. It has to be concluded that the lessons learned from the War impacted on the future of bombing and what tactics to use to gain optimum effect.

In order to storm a trench you would need eight men and one NCO  in the following formation:

Like many of the weapons developed for industrial scale use during the First World War, the Mills bomb defined a class of grenade that remained the standard British fragmentation grenade for over 55 years.

Written by Lisa Traynor, Curator of Firearms.

You can read more about the origins and use of the Mills bomb and other arms of the First World War on our collections online feature.

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