Every combat unit has its place in the order of battle and everything compliments each other. Combined arms is the art of using all the different weapons systems with each other in an effective and devastating way.
For example, tanks are very vulnerable to infantry armed with rockets and grenades. It is not difficult for an infantryman to disable a tank by blowing off a tread. Once a tank is disabled satchel charges and hand grenades are next. In an urban environment tanks are especially vulnerable to infantry because of all the places an infantryman can hide. A person buttoned up inside a tank has very poor visibility, which an infantryman can exploit. External cameras and sensors may change this but they will be susceptible to attack. Until then infantry will be needed to protect tanks from enemy infantry.
On the other hand infantry can be vulnerable to tanks. Tanks are big and powerful, very well armored and heavily armed with a cannon and machine guns. Infantrymen can be elusive and very hard to target by someone in a tank but if the Infantry are in fixed positions that can be easily targeted by tanks. . . you get the picture.
However, when tanks and infantry work together they are a fearsome team. No fortification is immune to them. Infantry can neutralize other infantry and the tank can destroy targets that are too tough for the infantry.
Tanks and infantry are not the only part of a combined arms team. Jeeps (or HUMMV’s), helicopters, jet fighters, Recon teams, and more can make up a Combined Arms team. Each asset can fulfill a critical role.
Smaller, faster units can cover the flank or range ahead to bloody the nose of the enemy while the rest prepare an ambush. Mortars, Artillery and Naval Guns can pound a target and inflict casualties on the enemy before the tanks and infantry attack it. Aircraft can also take a shot at the target before ground units are committed. For more precision a recon team can be sent in ahead of the main units to insure supporting arms are more accurate and the follow on units are more able to exploit advantages provided to them by terrain or weakness in the enemy line.
One example of more specialized Combined Arms teams is the Tank Killer team composed of fast moving, and lightly armored Hummvee’s. The Tank Killer teams will ambush an armored unit and then retreat before the enemy can act. In this way the enemy can be whittled down to size and demoralized. Four Hummers, two equipped with anti-tank missiles and the other two equipped with machine guns. As the second two open fire with machine guns the enemy tank crews will retreat back into their tanks (most tankers prefer not to be cramped up inside where they can’t see their surroundings) during those critical few seconds while the tankers are not watching, the missile gunners take aim and fire. By the time the tankers realize what is happening it is too late and the HUMMV’s are leaving.
Artillery, mortars, and naval guns are supporting arms. Alone they can be dangerous but at a distance they are even more so because they do not have to see the target to kill it. By determining the location of a target and their own location they can determine what angle to point their gun and which direction and how many charges to put into the round. The round arcs up and over hills, trees and other obstacles to fall into the enemy’s position. The longer the distance the lower the arc.
The range of artillery and naval gunfire is usually over ten kilometers. A Mortar’s range is usually less than ten kilometers. Of course there are always exceptions. Big guns (artillery and Naval Guns) can fire rocket-assisted ammo which can go even farther and the type of rounds vary, from flares to minefields.
Artillery and mortars often fire in groups of two or more. The spotter is responsible for telling the FCC (Fire Control Center or FDC Fire Direction Center) where the enemy is. One gun will fire and the spotter will adjust it until it is close enough to the enemy, all the weapons will adjust with the main one. At that point the spotter will say “Fire For Effect” and all the cannon or mortars of that unit will fire a volley of shells at the target. Of course a spotter might just instruct the FDC to fire for effect without adjusting if he is sure of himself and the artillery.
Against an entrenched enemy there are usually several options. WP or White Phosphorus can burn the enemy out and other rounds can create bigger craters, which are more likely to destroy bunkers and trenches. One mean trick is to fire a minefield on top of them. The minefield consists of numerous mines that shoot out a strand of wire. After a certain amount of time the mines arm and anything disturbing that wire will cause the mine to explode.
Of course a minefield like that can be cleared but the unit underneath it isn’t going to rush out to help someone nearby without heavy casualties.
When Supporting Arms are assisting an attack they will usually fire on the target until the ground forces are almost in danger from the supporting fire. When the ground forces begin their attack, the Supporting Arms will start firing behind enemy lines to prevent the enemy forces from retreating.
In the future, orbital weapons and cruise missiles could supplement the regular supporting arms. Starships in orbit could provide real time views of the target area as they fired on it with beams and missiles.
Of course a target that comes under fire can move, and if it is not heavily protected by fortifications this is the best defense.
Supporting arms are no different in this regard. Enemy radar can detect where the attack came from and can return fire with their own artillery if they are in range. This is called counterbattery fire and can get supporting arms involved in artillery duels. It is always best for the artillery battery or mortars section to relocate after firing a mission because they might draw fire. As technology gets better, counterbattery fire will become faster and more deadly. Just simply firing a mortar from an unprotected position could be fatal.
Attack aircraft actively seek enemy supporting arms, which further increases, the risk.
Most mortars are man portable, meaning they are carried by infantry units. Other mortars are towed behind trucks or jeeps and yet others are located inside armored personnel carriers. Obviously, the smaller the mortar the harder it is to find by enemy searchers but there is always enemy counterbattery radar. Newer (more expensive shells) are made of ceramics and are virtually undetectable to counterbattery radar.
Man portable mortars are more elusive but not as fast moving as the others. Most artillery cannon are towed behind trucks but there are some self-propelled canons, which are lightly armored tanks with an artillery cannon.
Tanks do not make good artillery units because they are designed to kill other tanks. The barrels are built differently and the angle they can fire at is not as versatile. An SP (self-propelled) gun on the other hand is not a good tank killer because they do not have turrets to engage an enemy to the side and are not heavily armored. The armor of an SP gun is to protect it against counter battery fire, which kills more with shrapnel than direct hits.
Mortars, regardless of transportation method, are high angle weapons, meaning the round goes almost strait up before it comes down. The mortar was designed in World War One to go up and come down in enemy trenches where artillery had a hard time hitting. The fact they were lighter than artillery made them a kind of Company Artillery unit and in the Marine Corps gives every infantry company a dedicated, indirect fire asset. If a Company Commander wanted to he could assign one mortar to each platoon but it would severely decrease their effectiveness.
At the Battalion level there are more mortars giving the Battalion commander his own dedicated, indirect fire asset to support whatever company needs it. Battalion mortars are of a heavier caliber, which increases their damage potential and range but decreases their mobility (although they are still man portable). The disadvantage of mortars is primarily their ammunition supply. An infantry unit cannot carry large amounts of ammunition.
Supporting Arms provide much more than the ability to destroy enemy units. Flares can provide illumination for a battlefield; artillery delivered mines can block or deflect an enemy advance. White Phosphorus can burn the enemy and it could provide a marker for attack aircraft. Smoke can conceal an attack or retreat and mark targets for aircraft. By firing on a runway, artillery can render it unusable for aircraft.
Aircraft are superior to artillery in most instances because they can provide more effective, more powerful munitions, like FAE or Napalm. Fuel Air Explosives are some of the nastiest munitions. A stream of gas is dispersed through the air by the munition, and then it is ignited over the enemy positions. The resulting explosion has a tendency to burn any unprotected enemy and suck all the air out of bunkers causing them to implode.
Napalm and White Phosphorus are also very vicious munitions that burn and cannot be put out by water or rolling on the ground. The burning stuff must be scraped off with a knife or something.
All things considered, a bullet is one of the cleaner ways to die and the military is usually concerned more with killing the enemy than how it is done.
Combined arms is the best method of killing the enemy effectively and with a minimum of friendly casualties.