Mortars have been used for hundreds of years, originally in siege warfare. Many historians consider the first mortars to have been used at the 1453 siege of Constantinople by Mehmed the Conqueror. A European account of the 1456 siege of Belgrade by Giovanni da Tagliacozzo said that the Ottoman Turks used seven mortars that fired "stone shots one Italian mile high". The time of flight of these was apparently long enough that casualties could be avoided by posting observers to give warning of their trajectories. However, earlier mortars were used in Korea in a 1413 naval battle when Korean gunsmiths developed the Wan'gu (gourd-shaped mortar) (완구, 碗口). The earliest version of the Wan'gu dates back to 1407. Choe Hae-san (최해산, 崔海山) (1380–1443), the son of Choe Mu-seon (1325–1395), is generally credited with inventing the first Wan'gu.
French mortar diagram from the 18th century.
Early mortars, such as the Pumhart von Steyr, were also large and heavy, and could not be easily transported. Simply made, these weapons were no more than iron bowls reminiscent of the kitchen and apothecary mortars whence they drew their name. An early transportable mortar was invented by Baron Menno van Coehoorn (Siege of Grave, 1673). This mortar fired an exploding shell, which had a fuse lit by the hot gases when fired. This innovation was quickly taken up, necessitating a new form of naval ship, the bomb vessel. Mortars played a significant role in the Venetian conquest of Morea and in the course of this campaign an ammunition store in the Parthenon was blown up (see diagram).
Engraving depicting the Venetian siege of the Acropolis of Athens
, September 1687. The trajectory of the shell that hit the Parthenon, causing its explosion, is marked.
An early use of these more mobile mortars as field (rather than siege) weapons was by British forces in the suppression of the Jacobite rising of 1719 at the Battle of Glen Shiel. High angle trajectory mortars held a great advantage over standard field guns in the rough terrain of the West Highlands of Scotland.
Coehorn-type mortars of approximately 180 pounds (82 kg) weight were used by both sides during the American Civil War. At the Siege of Vicksburg, General US Grant reported making such mortars "by taking logs of the toughest wood that could be found, boring them out for six- or twelve-pound shells and binding them with strong iron bands. These answered as coehorns, and shells were successfully thrown from them into the trenches of the enemy".
The mortar had fallen out of general use by the Napoleonic era and interest in the weapon was not revived until the beginning of the 20th century. During the Russo-Japanese War, Lieutenant-General Leonid Gobyato of the Imperial Russian Army applied the principles of indirect fire from closed firing positions in the field and, with the collaboration of General Roman Kondratenko, he designed the first mortar that fired navy shells.
The German Army studied the Siege of Port Arthur, where heavy artillery had been unable to destroy defensive structures like barbed wire and bunkers. The solution they developed was a short-barrelled rifled muzzle-loading mortar called the Minenwerfer, and was built in three sizes. Recognizing the advantages of the Minenwerfer in trench warfare, production was stepped up and, by 1918, the numbers had increased dramatically to 1,234 heavy, 2,361 medium and 12,329 light versions.
The Eprouvette was a mortar used to test the strength of gunpowder. It fell out of use by the middle of the 19th century.
Modern portable mortar
It was not until the Stokes trench mortar was devised by Sir Wilfred Stokes in 1915 during the First World War that the modern mortar transportable by one person was born. In the conditions of trench warfare, there was a great need for a versatile and easily portable weapon that could be manned by troops undercover in the trenches. Stokes's design was initially rejected in June 1915 because it was unable to use existing stocks of British mortar ammunition, and it took the intervention of David Lloyd George (at that time Minister of Munitions) and Lieutenant-Colonel J. C. Matheson of the Trench Warfare Supply Department (who reported to Lloyd George) to expedite manufacture of the Stokes mortar. The weapon proved to be extremely useful in the muddy trenches of the Western Front, as a mortar round could be aimed to fall directly into trenches, where artillery shells, due to their low angle of flight, could not possibly go.
The Stokes mortar was a simple weapon, consisting of a smoothbore metal tube fixed to a base plate (to absorb recoil) with a lightweight bipod mount. When a mortar bomb was dropped into the tube, an impact sensitive primer in the base of the bomb would make contact with a firing pin at the base of the tube, and detonate, firing the bomb towards the target. It could fire as many as 25 bombs per minute and had a maximum range of 800 yards (730 m) firing the original cylindrical unstabilised projectile.
A modified version of the mortar, which fired a modern fin-stabilised streamlined projectile and had a booster charge for longer range, was developed after World War I; this was in effect a new weapon. By World War II, it could fire as many as 30 bombs per minute, and had a range of over 2,500 yards (2,300 m) with some shell types.
The French developed an improved version of the Stokes mortar as the Brandt Mle 27, further refined as the Brandt Mle 31; this design was widely copied with and without license. About 700 Stokes mortars were acquired by Poland between 1923 and 1926. These weapons were the prototypes for all subsequent light mortar developments around the world.
Mortars today, while substantially similar in design to the Stokes mortar, are greatly improved versions; these offer a weapon that is light, adaptable, easy to operate, and yet possesses enough accuracy and firepower to provide infantry with quality close fire support against soft and hard targets more quickly than any other means.
World War II US Army propaganda movie footage of the 914-mm "Little David" mortar being prepared and fired.
The largest mortars ever developed were the Belgian "Monster Mortar" (24 inches; 610 mm; developed by Henri-Joseph Paixhans in 1832), Mallet's Mortar (36 inches; 910 mm; designed by Robert Mallet and tested by the Woolwich Arsenal, London, in 1857) and the "Little David" (36 inches; 914.4 mm; developed in the United States for use in World War II).
Although the latter two had a caliber of 36 inches, only the "Monster Mortar" was used in combat (at the Battle of Antwerp in 1832).
The largest mortars to see active use in modern warfare were the German 60 cm (23.6 inch) Karl-Gerät.
Improvised, or "home-made", mortars have been used by insurgent groups, usually to attack fortified military installations or to terrorize civilians. The Provisional Irish Republican Army used some of the best-known examples during the 1970s, 1980s and 1990s. The largest types came to be known as "barracks busters" and were usually constructed from heavy steel piping mounted on a steel frame. The largest had a calibre of 320 mm (13 in) and fired home-made rounds carrying from 80 to 100 kg (180 to 220 lb) of explosive.
improvised mortar tube.
As each tube fired only one round, mortars were usually deployed as a battery of four or six welded onto a steel frame. This was often concealed inside a van, such as a Ford Transit. The vehicle would be parked, pointing roughly at the target. A timer fired the propellant charges after a delay – this allowed the mortar gunner time to escape. After firing, a timer-operated incendiary device could set the vehicle on fire in order to destroy any forensic evidence it contained.
Well-known incidents using these weapons include the 1985 Newry mortar attack, when nine members of the Royal Ulster Constabulary were killed, and the Downing Street mortar attack in 1991. In the latter, the IRA launched three bombs at 10 Downing Street, the British Prime Minister's residence, during a cabinet meeting there. The only bomb that detonated landed in the building's back garden, and shattered the rear windows. Prime Minister John Major had to move to Admiralty House while repairs were effected.