The iconic Mills bomb was designed for grip, not for its famous fragmentation pattern.

Wars & Conflicts · Published 15 October 2026 Swipe more like this →

In short: The Mills bomb defined the modern hand grenade, yet its signature serrated exterior was never intended to aid fragmentation. Developed in 1915, this British weapon relied on internal explosives rather than its casing to wound. Its evolution reveals a complex history of trial, error, and adaptation across two world wars.

William Mills, a designer from Sunderland, patented the Mills bomb in 1915 at his Birmingham factory. The design was heavily influenced by a failed prototype from Belgian captain Leon Roland, which the British War Office had rejected for being unreliable. Mills refined the concept, moving from a spherical shape to an oval body. Contrary to popular belief, the iconic external serrations were not meant to break into shrapnel upon detonation; they were added simply to help soldiers maintain a firm grip on the weapon when their hands were covered in mud.

The grenade was classified as a defensive weapon, intended to be thrown from behind cover. Because fragments could travel significantly further than the blast radius—often exceeding the 15-meter throwing range of a competent soldier—it posed a danger to the user if thrown in the open. To manage these risks, the British military implemented strict color-coding systems. A red band around the base plug indicated a live detonator, while various colored bands around the middle identified the specific explosive filler, such as Amatol, Baratol, or Trotyl, which were adjusted over time to suit different climates like the heat of Mesopotamia.

The weapon's versatility led to various adaptations, including rifle-launched versions. Early models used a steel rod inserted into the rifle barrel, but the intense pressure often caused barrels to bulge or split. This eventually gave way to cup-type launchers, which allowed the grenade to be fired without damaging the firearm. Over decades, the design saw constant refinement, such as reducing the fuse delay from seven seconds to four seconds during the 1940 Battle of France to prevent enemies from throwing the grenades back. While the No. 36M remained a staple of British service until the late 1960s, it was eventually replaced by modern designs featuring coiled wire within smooth casings.

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