Object Title

No. 5 Mk.1 Mills Bomb

No. 5 Mk.1 Mills Bomb


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.

Use and effect

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), 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 fuze, and a cap chamber housing the initiating percussion cap, along with a base plug key. 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.'

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. Consisting of eight men and one N.C.O. in order to storm a trench you would need to be in the following formation:


No 1) Rifleman equip with three bombs for emergency, his primary task was to 'precede the party down the trench and by means of his bayonet repel enemy onslaught.'

No 2) Bayonet man, who passed back messages from the rifleman to the thrower.

No 3) The first thrower, he carries up to 12 bombs, 'his duty is to bomb the main trench as far forward as possible.'

No 4) Acts as carrier to the thrower assisting throwing where possible, his primary duty is to bomb communication trenches.

No 5) The N.C.O. who is also equip with a few bombs.

No 6) The second thrower whose task is to also bomb communication trenches, however he stops and bombs the communication trench until another section from the rear take over. He also replaces the third man if he becomes a casualty.

No 7) Assists the sixth man as a carrier and auxiliary bomber.

No 8 and 9) Are rifle bombers. They carry 12 bombs and an ample supply of rods (which are inserted into the grenade at one end and into the barrel of the rifle at the other) so if necessary they can use the throwers bombs and vice versa.

The third and fourth men should be together if possible and the eighth and ninth, but bunching the section together is to be avoided as the whole party may suffer from one bomb.



Country of manufacture Britain
Date entered service 1915
Effective range 18 m (20 yd) (kill zone)
Manufacturer Mills Munition Factory
Overall length 10 cm (3.9 in)
Primary operator Britain
Weight 760 g (1 lb 10 oz)


Lisa Traynor