No. 106 Fuze

Number 106 Fuze was the first British instantaneous percussion artillery fuze, first tested in action in late 1916 and deployed in volume in early 1917.

Britain entered World War I with a policy of using shrapnel shells for its field guns (13 pounder and 18-pounder), intended to burst above head-height for anti-personnel use. British heavy artillery was expected to attack fortifications, requiring high-explosive shells to penetrate the target to some extent before exploding. Hence British artillery fuzes were optimised for these functions. Experience of trench warfare on the Western front in 1914–1916 indicated that British artillery was unable to reliably destroy barbed-wire barricades, which required shells to explode instantaneously on contact with the wire or ground surface: British high-explosive shells would penetrate the ground before exploding, rendering them useless for destroying surface targets.

British No. 100 and later No. 101, 102 and 103 nose "graze" fuzes available in the field from August 1915 onwards could explode a high-explosive shell very quickly on experiencing a major change in direction or velocity, but were not "instantaneous": there was still some delay in activation, and also had limited sensitivity: they could not detect contact with a frail object like barbed wire or soft ground surface. Hence they would penetrate objects or ground slightly before detonating, instead of on the ground surface as required for wire cutting. These graze and impact fuzes continued to be used as intended for medium and heavy artillery high-explosive shells.

Up to and including the Battle of the Somme in 1916, British forces relied on shrapnel shells fired by 18-pounder field guns and spherical high-explosive bombs fired by 2-inch "plum-pudding" mortars for cutting barbed-wire defences. The disadvantage of shrapnel for this purpose was that it relied on extreme accuracy on setting the fuze timing to burst the shell close to the ground just in front of the wire: if the shell burst fractionally too short or too long it could not cut the wire, and also the spherical shrapnel balls were not of an optimal shape for cutting strands of wire. While the 2-inch mortar bombs cut wire effectively, their maximum range of 570 yards (520 m) limited their usefulness.

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