Stokes 3-inch Trench Mortar

The Stokes 3-inch Trench Mortar was a bipod-mounted light mortar weapon designed and developed by English engineer Frederick Wilfred Scott Stokes, later to become Sir Wilfred Stokes KBE. It was adopted by the British Army in mid-1915 and would remain in service for more than two decades.

While existing howitzers were extremely capable against entrenched enemy troops, while also carrying significant physiological effects,  they were large, heavy and cumbersome. As the stalemate of trench warfare continued, the British Army called for a light mortar to be developed that was both effective and mobile enough to be used as an infantry close-support weapon.  The Germans, meanwhile, were also also developing a new light trench mortars themselves – the 7.58cm Leichter Minenwerfer.

Stokes had a prototype of his design developed as early as December 1914 and it was soon undergoing testing to evaluate it effectiveness. Although trials were successful, the design was initially rejected because the weapon was unable to use existing stocks of mortar ammunition held by the British. After some controversy, this decision was overturned and the 3-inch Stokes Trench Mortar, Mark I was eventually put into production and was soon being used by British troops at the front. The weapon weighed almost 110lbs in total and required a two-man crew to use it – one to load the ammunition and the other to control elevation and trajectory. 

The mortar was a smooth-bore, muzzle-loading weapon that was capable of firing up to 30 rounds-a-minute by a highly-trained crew at an effective range of over 750 yards. An amatol filled high-explosive cylindrical shell weighing 11lbs, which had a propellant charge and igniter attached to its base, was dropped down the mortar tube and fired on impact with a striker at the bottom.  Range and trajectory was adjusted by the amount of propellant charge used and the elevation of the barrel. Despite its name, the bore of the mortar was actually 3.2 inches.

A base plate that weighed 28lbs was used with the mortar, which helped reduce recoil. For mobility, the Stokes mortar could be broken down into three components – the barrel, baseplate and bipod. This enabled it to be moved forward to support and consolidate infantry gains if needed.




Official NameMortar, Trench, 3 InchRate of Fire25-30 rounds per minute
Weight110 lbsElevation45°-75°
ShellHE 10lb 11oz (Amatol filled)Effective Range750 metres
ActionTripMaximum Range800 metres
Feed SystemMuzzle-loading