The mortar as a weapon is one dating back to about the 12th Century or perhaps even earlier and most always credited to the Chinese. The design concept was simple in nature and based on the shape of the apothecary mortar - a heavy shallow bowl. Mortars were then made in all sizes, large at first then smaller, portable devices for warriors who needed a personal weapon for short-range bombardment. As time went on, more powerful gunpowder and exploding shells were developed along with improved metallurgy for the barrel. Generally speaking, mortars are smaller than artillery weapons but fill a need for "plunging" fire against fixed enemy positions and strong points.
The Soviet Army used many sizes of mortars during the Great Patriotic War and the heaviest was the M1943 (MT-13) firing a 160mm shell. Developed in 1943, a major problem was found while trying to load the weapon it needed the 90lb shell dropped down the 9 ft (3m) firing tube. This herculean effort was found to be non-practical, forcing the weapon to be redesigned. This needed retooling allowed the barrel to be tilted down to a horizontal position for breech loading. The loading system also needed a new heavy duty recoil system to absorb the shock of the firing 160mm shell, an action that forced the base plate far into ground. To counter this force, a large concave thick steel plate was used to spread the downward energy created by the muzzle velocity. The weapon sat on a tripod consisting of the two tow wheels and the base plate making the M1943 one stable firing platform. Loading the weapon required the barrel to be unhinged, allowing it to tilt forward and expose the breech from the base plate. The 90lb shell was then loaded and the breech was closed. The barrel or tube is then cranked to the required mission elevation and is able to be fired at 10 rounds per minute by a trained and rested four man crew. Muzzle velocity was listed at 804 feet per second. Effective range was approximately 5,600 yards.
The Soviet Army assigned the M1943 to its Brigade size units due to its range. Larger artillery with much greater range was assigned to Division size military units. The Brigade was divided into four smaller units called Battalions that had 8 - M1943 mortars assigned to each, making the Brigade's strength 32 M1943's and including its applicable crews and towing vehicles.
The Soviet Army used the M1943 against Germany and effectively with their attack on Berlin in the heavy street-to-street fighting that ensued. After the war, the M1943 was sold to Soviet-allied states and nations including Bulgaria, Czechoslovakia, Poland, Romania and Ukraine plus Syria abroad.
The M1943 was eventually replaced in Soviet post-war service by the M-160 160mm heavy mortar.