This grenade was meant to be thrown from a trench, often while kneeling or crouched, with very little room to move. Soldiers had to clear the trench wall and get it into the enemy position before it could be thrown back at them. That challenge explains both the design of the British No. 3 Mk I grenade and why it was quickly replaced.

At first glance, the grenade appears unusual: a metal body about 5 inches long and roughly 3 inches in diameter, mounted on a 5-inch wooden cane handle. Its form reflects early First World War thinking about how grenades should be thrown — before trench fighting exposed the flaws in that approach.

Why It Mattered

Once fighting on the Western Front settled into trench systems, grenades became essential weapons for clearing enemy trenches at short range. Soldiers needed grenades that were compact, reliable, and safe to use from confined positions.

The No. 3 Mk I represents an early attempt to meet that need.

Design and Development

Britain entered the war without a modern hand grenade. The original No. 1 grenade, from which the No. 3 was derived, was designed at the Royal Laboratory. Its design was influenced by Japanese grenades observed during the Russo-Japanese War, based on reports and samples provided by General Sir Aylmer Haldane, a British observer during that conflict.

Japanese grenades used long handles to improve throwing distance and stability. While effective in open terrain, this feature proved problematic in trenches.

From the No. 1 to the No. 3

The long wooden handle of the No. 1 grenade created hazards in narrow trenches. When soldiers reached back to throw, the handle could strike trench walls or parapets, causing the grenade to be deflected or to fall back into the thrower’s own position.

The No. 3 Mk I shortened the handle to make it easier to throw from kneeling or crouched positions. Although this reduced some risks, it did not solve the fundamental design issues.

How It Was Used

The grenade employed a percussion ignition system. After being armed, it detonated when it struck a hard surface.

Under ideal conditions, a strong soldier could throw a grenade of this type approximately 25–35 yards (23–32 metres). In trench fighting, throws were often much shorter due to limited space and the need to remain under cover.

On detonation, fragments from the metal body could kill or seriously wound enemy soldiers. In the confined space of trenches, blast and fragmentation effects were especially severe.

Problems in Combat

Despite its modifications, the No. 3 Mk I performed poorly in combat. German prisoners captured at Ypres in January 1916 reported that wooden boards lining trenches could deflect the grenade. In some cases, deflected grenades could be picked up and thrown back.

Production also posed difficulties. The grenade required a special detonator that could only be manufactured by ordnance factories, resulting in severe shortages at the front.

A later variant, the No. 18, was designed to use a more commonly available detonator. By that stage, battlefield experience had already shown that the long-handled grenade concept was ineffective.

Replacement

By 1915–1916, British forces adopted compact, handle-less grenades, most notably the Mills bomb. These designs were safer to use from confined positions, employed timed fuses rather than impact detonation, and proved far more effective in trench warfare.

The No. 3 Mk I was rapidly phased out.

Technical details

• Designation: No. 3 Mk I Hand Grenade
• Period: First World War (c.1915)
• Body length: Approx. 5 inches (12.7 cm)
• Body diameter: Approx. 3 inches (7.6 cm)
• Handle: Wooden cane shaft, approx. 5 inches
• Ignition: Percussion (impact-detonated)
• This grenade is inert.