The Mortar Against Armor

Ask the average tanker what threat mortars are to his tank and he will more than likely tell you. "None." The mortarman confidently replies, "If we hit you, we'll kill that tank." Who is right? Can the mortar be a threat to tanks? Well, let's look at the mortar's boast. First, mortars most commonly used by Western armies are the 81-mm or 3-inch, the 107-mm or 4.2- inch, and the 120-mm. All have shells available with delay fuzes designed to explode after penetrating hard surfaces. Because of the steep trajectory of the mortar shell, a hit strikes the top of the tank. where the armor is not over two inches thick. Usually the top includes hatches, air intakes, and optics. It is the weakest point of the tank, therefore a hit on the top should make the tank ineffective. But, with the equipment in the U. S. Army inventory, a mortar will not hit a moving armored vehicle except through luck or massive use of ammunition. Why? The mortar is a four-part system, including a forward observer who can see the target and report its location, a fire control center to compute the sight and charge settings, the gun and crew, and - last of all - the ammunition. To hit a moving target is like shooting geese. A consideration of speed and time is a prime requirement. A vehicle moving at only 12 mph (20 kph) moves 333 meters every Bomblet Rounds Like a shotgun, the unguided mortar shell depends on the dispersion of its bomblets to increase probability of a hit within a 70-140 meter "footprint" circle. minute, 5-1/2 meters per second. A modern tank can kill within 10 seconds after target acquisition. A 4.2-inch mortar typically requires 15 seconds for the call for fire, 15 seconds for the computations, 20 to 30 seconds for the gun crew to aim and prepare ammunition, and an additional 20 to 30 seconds while the round is in the air. During this 70 to 90 seconds, the target has moved 400 to 500 meters. These time estimates assume that the mortar section is set up and ready to shoot. If it is not, times and inaccuracies go up. Our goose hunter/observer's chances of having the correct lead are remote. Can we improve these odds? I will not argue that they should be. If a system can kill the enemy, or force him to accept our policy, we should use ARMOR - I 1

Guided Mortar Rounds it, as long as it is not counterproductive. Mortars can fire from defilade, they have a good effective range, have a potential for fast rates of lire, and have a low cost per weapon. What the.mortar lacks is a high probability of hitting the target. Any change in speed will help. By improving the MlWM125, it would be possible to provide it with "shoot-and-scoot" capability. The separate lire control is eliminated in those improvements. Speed increases, allowing it to better keep up with the new tanks, at least in abounding situation. With an improved carrier we can cut the time from targct acquisition to weapon firing to 30 seconds, even while the vehicle is on the move. But we cannot improve upon the long flight time of the mortar shell in its hi.&-angIe trajectory. The German "Bussard" 120-mm mortar round begins searching for targets on the way down, using built-in guidance, which may come from radar, infrared, or laser designation. But can such autonomous guidance systems tell the difference between friend or foe? We are stuck with a 20- to 30- second flight time, so the target will have time to move about 330 meters into brush, a treeline, or behind the crest of a hill. It seems that in order to get a hit, we must lire a better shotgun, or figure out away to guide the round as it descends. "Smart" Mortar Rounds and Bomblet Carriers As a matter of facl, some are trying both of these approaches. Spain, Greece, Sweden, and England have developed mortar rounds that greatly increase the usefulness of the mortar against moving targets. The Spanish and Greek mortar rounds are less expensive, but do not eliminate the problem of leading the target. These rounds are actually camers for 15 or 20 bomblets, or grenades. When over the target, the shell distributes the bomblets in a pattern around the aiming point. Thus, while any single round tired may have a range probable error of 20 meters and a deflection error of 10 from the aiming point, at least one of the grenades should hit. For a stationary target, this is fine. However, to expect the observer to predict where the target will be in one minute will still be difficult. The Spanish round, manufactured by Espin, is a 120-mm round containing 15 bomblets in the long-range version and 21 in the short. Each submunition will penetrate 150 mm of armor and has an effective radius of 20 meters against per- 72 ARMOR - November-December 7989 sonnel. The bomblets are spread over a 60- by 70-meter area. The Greek version is a 107-mm shell that carries 20 grenades. Armor penetration is 80 mm, enough to break through the top of most armored vehicles. The dispersion "footprint" varies from 70 to 140 meters in diameter. Lethal radius against troops is three meters. Against infantry, these would be more effective than conventional rounds. The Swedish and British antiarmor mortar rounds are more sophisticated, and offer a better chance of a hit. These self-guided antiarmor projectiles use sensors to detect the vehicle, identify it as a target, and c guide themselves to the target even as the victim moves. The sensors may use infrared, millimeter-wavelength radar, a laser designator, or a combination of these methods. Strix, developed in Sweden, is a 120-mm round with a range of 600 to 8,000 meters. It is carried in two sections, and can accommodate a rocket booster for extra range. It will penetrate over 400 mm of armor, providing a useful degree of overkill. The British round, called Merlin. is the most compact. It is designed for an 81-mm system. and is said to be usable by any modern 81- or 82- mm mortar. It searches within a 300- by 300-meter area. using an active millimeter-wave radar capable of detecting the target under trees or camouflage. It can defeat 12 inches of armor. The Guided Antiarmor Mortar Pmiectile (GAMP) should be operational this year. Its range is about 4000 meters. West Germany had been working on a 120-mm version of GAMP, called Bussdrd. It was to have an interchangeable guidance system, so that the observer can use infrared, radar, or laser designation. Range was to have been 800 to 5000 meters. Successful firings were reported in 1983. Are Smart Rounds Smart Enough? Smart munitions will allow a mortar to engage a moving target with a decent chance of a hit. However, some have raised objections to the GAMP, on the grounds that the guidance system cannot tell the difference between friend and foe. It may be possible to develop a fiber-optic-linked round, similar to the FOGM, but the operator would have only 10 seconds or so to acquire the target and home in on it, making it appear to be an improbable approach. How could a human operator reliably tell the difference between a T-72 and an M2 Bradley in two or three seconds, from the top, and at a range of 1000 meters on a fuzzy TV screen? Perhaps it would be better to train the forward observer in the characteristics of the round and equip him in such away that the round won't notice him. L. B. Holley, in his Ideas arid Wcaporis, states that we must always remember that new weapons create the need for new tactics. He was not speaking of a mere improvement, like from the M3 Stuart to the M4 Sherman, but something like the change from the smoothbore musket to the rifle. The combination of the mortar carrier capable of shooting from a brief halt, and the antiarmor round, is a comparable change. It alters completely the abilities of the system, and creates anew weapon. It does at least require that we consider new tactics and the organizational expression of those tactics. To emphasize the point, we should remember that, in the 1940 Battle of France, the French had more tanks than the Germans. Generally, the French tanks had thicker armor and bigger guns. The Germans won, in large part, because they organized their tanks better. Correct tactical use of a weapon requires correct organization. An improved M1M or M125 mortar carrier, armed primarily with GAMP, would be able to travel cross-country at about 25 kph and kill armored vehicles between 500 and 6OOO meters away, depending on the eventual range of the round. The improved vehicle has limited lethality against light armor inside of 10oO meters. Its own protection will not allow it to close with Warsaw Pact light armor. In away, it is analogous to a sniper, powerful but vulnerable. The tanks now in the inventory are faster cross-country. Their fire is fast and deadly out to 2000 meters. They have the ability to survive against most fire, most of the time. Compared to the improved mortar carrier, the tanks are submachine gunners, close-in brawlers. Brigadier Richard Simpkin, the late British armor authority, advocated tank destroyer/fire support vehicle pairs. Looking at the two types as 1 just have, perhaps he indicated how we should proceed. Suppose, therefore, that we organize a platoon as three pairs, each pair including an MTB and an improved mortar carrier (IMC). The IMC attacks long-range targets. The tank provides close-in shock and protection. The platoon leader has enough units for fire, maneuver and reserve. As we saw earlier, the mortar is a four-part system. It is not complete without observers. Each platoon also has three scout/forward observer teams. They would be mounted on small vehicles, such as ARMOR - November-December 7989 13 motorcycles, ATVs, or even something like the WASP individual flying device. These troops must remember that their primary weapon is the mortar. Under more static conditions, they patrol awes-sively, seeking to find the enemy. Thus the platoon has combat intelligence and the muscle to do something with it. It is a true combined arms unit. The company would be composed of four platoons. Two platoons are on the firing line, one is reserve (recalling that reserves win battles), and one is replenishing. Headquarters platoon consists of a pair of Bradleys, to give the commander room for work and for his extra radio equipment. Headquarters also carries the antiair responsibility. Concept of Employment To see how this would work in combat, let's look at a possible action. A Soviet mechanized infantry battalion with an attached tank company moves westward. Probing eastward, with the mission of finding and delaying or stopping the enemy, is anew type armor company. The Soviets have 33 BMPs, 10 T-72s, and four BTR mortar carriers. The Americans have 12 Mls, 12 IMCs, two M2s, and 36 motorcycles. First and second platoons are forward, third and fourth behind. The scouts are out about XXK) meters ahead of their platoons. The reserve platoons trail by about loo0 meters, depending on cover and terrain. Visibility is average for Central Europe, that is. about 3OOO meters, except for the woods and hills. Both sides are moving at about 250 meters per minute, a closure rate of 500 meters per minute. The scouts first see elements of the Soviet forces 6000 meters ahead of the main line mortars and tanks. Calls for fire go out at 5000 meters, two minutes later. Mortar tracks stop, fire a first round and move out again, while the tanks take covering positions. Range is down to 4500 when the first volley strikes. Four BMPs and a T72 stop, hit and smoking. The next wave of rounds comes in, then a slow steady rain. The closure rate of the two forces has slowed, on the American side because of the halts to fire, on the Soviet because of deployment from march. For about every three rounds fired, a vehicle is hit and knocked out of the battle. His tanks have no targets yet, his mortars have just started to dcploy, but have no one to give them the positions of the NATO forces. The scouts are moving at a crawl, literally, as they play hide and seek from ditches, trees, and bushes. Still, their calls for fire and sitreps go back. As long as they can see and report, they are effective. Only 10 minutes after first sighting, the range is down to 2000 meters. The tanks start to engage, and the company commander has ordered the reserves to open fire. By this time each of the six lead platoon mortars has moved and fired 10 times. If they fired two rounds each time, that was 120 GAMPs. Now, with the reserves concentrating on the remnants of the tanks, the enemy force has ceased to exist. The stragglers get hit by the tanks. No Soviets make it to within loo0 meters of our company. At a rate of 250 meters per minute, it takes only 10 minutes to move to point-blank range through the effective range of our tanks. Use of cover and concealment may reduce the actual exposure time to three or four minutes in 10- to 20- second glimpses. Scouts, hidden ahead of the firing line, will be better able to see targets and'call for fire, or even cue in the platoon's tanks. In the example we have just seen, if the tanks had to wait until the Soviet battalion was 3OOO meters away to open fire, some ol' the targets would have made it to under loo0 meters range, that is, to effective range of a BMPs 71mm gun. There simply is not enough time to shoot, move 100 meters, move into a position, acquire a target, move turret up, fire, back out, and repeat the process more than about 20 times in a 10-minute time span, even assuming that a target will present itself at the time that our forces are ready to fire in the new position. One of the most important lessons of the NTC is how rapidly the range closes. One of the other lessons is how important it is to have scouts and outposts to give early warning and to begin to attrit the enemy. Properly organized and equipped, the mortar can be an equal partner to the tank. To make it so, we must break down some of our old ideas on the weapon and imaginatively develop all of the mortar's promise. Sergeant Gilbert Warner served 7 years in 4.241. mortar sections, including service with the 11th ACR and 3-63 Armor in Germany and the 4-40 Armor at Fort Carson, Colo. His jobs included chief computer and section leader. He currently lives in Newport News, Va.. and is assigned to the 329th Transportation Co. 14 ARMOR - November-December 7989

Vehicle Recognition Quiz 4. 5. 6. Answers on Page 49 ARMOR - November-December 7989