South Korea has developed a self-propelled, automated 120mm mortar system. This system uses a more robust recoil system and computerized fire control that automatically adjusts the mortar's aim to hit the GPS coordinates of a designated target. This technology was introduced by the Israelis as Cardom in 2003 and widely adopted, improved and copied since then. The Cardom mortar system was a revolutionary computerized 120mm mortar with an improved recoil system that could be mounted on light and medium armored carriers. Its state of art fire control system connected with a suitable battle management system can provide accurate, effective and immediate fire support for infantry up to 7 kilometers distant. The manufacturer claims “first round on target” takes less than 30 seconds and the highest maximum rate of fire of 16 rounds per minute. The major innovation of Cardom was its automation. Forward observers can transmit digital target location information to the Cardom mortars, which automatically use a system of small electric motors to precisely aim the mortar tube. The first customer for Cardom, in 2002, was the Israeli Army and the troops found the CARDOMs a big improvement over older mortar designs. The U.S. and many other nations have since adopted Cardom.
The South Korean system replaces the 1980s era K242 self-propelled M30 107mm mortar. The American M30 was introduced in 1951, replacing a less effective M2 107mm mortar. Both South Korean 107mm and 120mm self-propelled mortars are mounted in the locally made M200 armored vehicle. The M200 is an improved version of the 1950s American M113 tracked armored vehicle.
In addition to a much more effective Cardon mortar system, Americans and Israelis both developed GPS guided 120mm mortar shells. In 2010 the U.S. adopted the American ATK system. In development since 2006, ATK uses a guidance system that replaces the fuze, which is screwed into the front of the shell, with a larger fuze containing the GPS and little wings that move to put the 120mm mortar shell closer to the target. All you need to convert existing 120mm mortar shells to GPS guidance is the ATK fuzes, which handle the usual fuze functions (setting off the explosives in the shell) as well as the guidance functions.
To use the ATK GPS system, you place each fuse into a device that transfers the target GPS coordinates, then screw the fuze into the shell, and fire the shell. It would also be possible to program each fuze once it is screwed into the shell, via a metal probe that fits in a hole in the fuze, transfer the data, and signal that that the transfer was accurately made. The GPS guided fuze can put the shell within 6-10 meters (20-30 feet, and usually much less) of the coordinates entered.
Because of the GPS fuze, 120mm shells just got a lot cheaper and easier to use. This is particularly crucial for 120mm mortars, which are used by units close to the front lines, where not a lot of ammo can be carried, and resupply is riskier since the enemy is so close. A guided 120mm shell means fewer shells getting fired to get the job done. Most vehicle mounted 120mm mortars carry about fifty 120mm shells and those vehicles can carry a dozen or more of ATK fuzes to turn any of those fifty shells into a GPS guided versions for use against targets that require only one or two shells rather than a barrage of a dozen or more shells landing over a wider area.
Unguided mortar shells cannot put the first round very close to the target, and require firing several rounds to adjust aim before one gets on on target. A guided mortar round is very useful in urban warfare, where a miss will often kill civilians. The 120mm mortar round has about 2.2 kg (five pounds) of explosives, compared to 6.6 kg (15) pounds in a 155mm shell. The smaller explosive charges reduce collateral damage to civilians. Normally, an unguided 120mm shell will land anywhere within a 136-meter circle (on the first shot). All GPS guided rounds land within a ten-meter circle. The GPS round is popular with the troops as are the earlier GPS guided 155mm artillery shells, 227mm rockets and JDAM bombs.
Mortars were a very effective infantry weapon and most nations equip their troops with 120mm mortars as well as larger numbers of smaller caliber (50mm-82mm) mortars that are carried by infantry. Oddly enough the modern mortar was invented by Britain in 2015, during World War I, and widely adopted and improved after World War I. The American 107mm was based on the British four-inch (102mm) mortar. The 120mm mortar was invented in France during the 1930s and widely copied and used ever since.
The original 120mm mortar was too heavy, at 150-200kg (330-440 pounds) for the troops to carry long distances, but it was lighter than regular artillery and as effective as the 105mm howitzers which provided most of the firepower during World War II. Some 120mm mortars were mounted on wheels and could be pulled by horses or troops. In Western armies the 120mm and 107mm mortars were often carried in light trucks or jeeps and set up next to the vehicle for firing. Some of these heavy mortars were mounted and fired from armored personnel carriers, which were first used during World War II.
The US did not have a 120mm mortar during World War II and only had a 107mm (4.2 inch) model because that weapon was designed just for delivering chemical shells. Since chemical weapons were not used during World War II, with a few minor exceptions, the 107mm mortars didn't have much to do except deliver smoke shells, which some considered a "chemical" weapon, even though they provided concealment for friendly troops rather than casualties among the enemy. By the end of World War II the 107mm mortar was firing high-expolsive shells most of the time. The illumination shell was available after World War II.
By 1944, it was recognized that the M2 4.2 inch (107mm mortars) were useful as artillery and they were used as such, even though they had a range of only 3-4 kilometers. Each "chemical" battalion contained 32 mortars and these were assigned to corps. This was quite different from the practice in other nations, where regiments were given 120mm mortars. One benefit of their past mission was that the battalions were equipped with white phosphorous (WP) shells. The WP shell created a lot of smoke, but the burning phosphorous caused nasty casualties. The Germans made noises about illegal use of "chemical weapons" when they realized what WP could do, but this did not result in the use of chemical weapons in retaliation. Nor were the Germans able to use many WP shells themselves because of raw material shortages.
As the war went on, it became the American practice to assign one mortar company (eight 4.2" mortars) to an infantry battalion. Not all infantry battalions got mortars, preference being given to units involved in attacks. An improved 107mm mortar, the M30, was developed after World War II and widely exported. Many nations still use it and the Americans did not adopt the 120mm mortar until 1991 when the Israeli Soltam was selected to replace the 107mm models.