Generally the mortar was just a metal cylinder attached to a bipod mount. There was a projecting pin inside the base of the tube so that when the mortar bomb was slid down the tube a detonating charge was set off that flung the bomb into the air. The bomb itself was usually made of cast iron and varied somewhat in size and design. They were originally equipped with timed fuses but these were replaced quickly by impact fuses. Mortars themselves could be found in several, slightly varied shapes and sizes.
Mortars were used to hurl their bombs high into the air at steep angles. The desired effect was that the bomb would fall from directly above, landing right on the enemy. This kind of weapon was made very useful in trench warfare, as you could attack your enemy without leaving the safety of your trench. Mortars were used to take out enemy machine gun posts, suspected sniper posts or other designated features. Larger mortars were occasionally used to cut enemy barbed wire, generally in situations where field artillery could not be used.
Although the British managed to produce the most effective design, the Germans were the first to utilize their potential during WWI. German military observers of the Russo-Japanese war left with a renewed respect for the mortar bombs they’d seen deployed. They began stockpiling mortars in the few years prior to the war and by the time war had hit, they had around 150 mortars available to them. The German’s had envisaged how useful mortars would be against the eastern fortresses of France and this was their initial motive for stockpiling them.
The French and British were caught completely off guard by the reinvention of the mortar. The French reacted initially by digging up ancient stockpiles of mortars from the Napoleonic times (known by the Brit’s as “Toby” mortars after the British officer who had the idea of securing these stockpiles) But Britain, were in a much worse position as they were completely without the mortar due to the absence of it’s use in their last war, the South African war 1899-1902.
Even after the demonstration of the mortar’s effectiveness by the German’s, there were still elements inside the British High Command that had doubts about the mortar’s cost-effectiveness. It took the Prime-Minister, David Lloyd George who came in late 1915 to push its manufacture through for it to be taken seriously. But once they’d grasped just how effective the mortar could be, everyone was behind it whole-heartedly.
The German word for mortar, “minewerfer”, literally means mine-thrower. These were designed in 1908-09. Their rifled mortars came in three sizes: light – 7.6 cm, medium – 17 cm, and Heavy – 25cm. Heavy mortars weighed around 96 kg and were mounted on field carriages.
The first British mortar, compared to the Germans’ Heavy 25 cm, was a relatively small design, being just over 10 cm.
Although the Germans had a huge head-start in the way of mortars, the Allies soon caught up and eventually surpassed the Germans in mortar excellence. Mr F.W.C. Stokes – later to become Sir Wilfred Stokes KBE – saved the day for the British in January 1915. That was the month that he came up with a simple yet highly effective design. It consisted chiefly of a smooth metal tube fixed to a base plate (to absorb recoil) with a light bi-pod mount. When a bomb was dropped into the tube an impact sensitive cartridge at the base of the bomb would make contact with a firing pin at the base of the tube, thereby ejecting the bomb. This soon became British army standard issue as well as to their allies. It was used effectively for over a decade. Most of the modern mortars are the descendants of the Stokes.
The mortars of the Germans and the Allies were of around even effectiveness and played a big part in the outcome of WWI.