The Mills bomb, officially called the No. 5 hand grenade, is one of the most iconic weapons of the 20th century. Named after its British inventor, William Mills, who drew inspiration from the Belgian Roland grenade (1912), the bomb was introduced into British Army service in May 1915. Weighing 1.25 pounds and fitted with a four-second delay, it featured a distinctive serrated cast-iron outer casing. The design was to aid grip rather than fragmentation—fragmentation did not reliably follow the serrated sections—but the steel shards propelled by the Baratol charge (a mixture of TNT and barium nitrate) nevertheless retained lethality to 80 yards and beyond. A competent thrower could deliver the grenade accurately to ranges of 15 to 20 yards, and the grenade truly excelled in brutal trench-clearance operations. During British attacks, individual “bombers” would carry up to 24 Mills bombs in green canvas buckets, each man acting almost as a form of close-quarters artillery. The definitive Mills bomb iteration was the popular No. 36M of 1917, shown here, which was waterproofed with shellac. Lethal, handy, and plentiful (75 million were made between 1915 and 1918 alone), the Mills bomb was the standard British grenade until 1972, its longevity a testimony to the success of its design.
Chris McNab is a military historian based in the United Kingdom. His latest work is The Book of the Poppy (History Press, 2014), commemorating the recent centenary of the onset of World War I.
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This article originally appeared in the Spring 2015 issue (Vol. 27, No. 3) of MHQ—The Quarterly Journal of Military History with the headline: Mills Bomb: Trench Terror
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