Object Title

Number 5 'Mills' hand grenade

Number 5 'Mills' hand grenade


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 I 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. However due to the nature of explosives they failed to do so. However, by default they did provide a firm grip in the wet conditions of the trenches.

Use and effect

To ignite the charge, the safety pin had to be removed and the lever released. In doing this the lever caused the striker to drop onto the .22 calibre blank cartridge, creating a flash that in turn ignited the grenade's fuse.  Originally manufactured with a seven second delay, this was shortened to four to five seconds, so the enemy did not have time to take cover, or throw the bomb back.

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

These grenades arrived in parts via wooden chests and were assembled and armed in the trenches. One of the processes involved would be to smear the pin in grease or Vaseline, to protecting against the elements of the Western Front, reducing the risk of rust and the pin seizing. Arming them was done at a distance, often from behind sandbags. This was a risky task as 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.'

Lack of range was a reoccurring problem. This was temporarily fixed by introducing the No.23 Mark I in 1916. The base plug was replaced with a threaded rod which could be inserted a rifle barrel and fired by means of a blank cartridge. However this in time ruined the bore of the rifle.

These grenades were an essential part of trench warfare, in particular during raids. Interestingly, notes from a bombing course that took place at School of Arms at 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:


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