Armchair strategists spend a lot of time discussing the virtues of various assault rifles or which tank is the studliest. But at the end of the day, artillery is King of the Battlefield. Where the big guns land, the earth moves. Soldiers stuff their ears but sometimes end up with bleeding eardrums. There are flashes, smoke and the air becomes a hailstorm of jagged metal. Half of all combat casualties in World War II were caused by artillery. And for the infantry the worst part is there is nothing he can do except hug the earth and hope for it to stop. Artillery kills and maims in quantity. It is the infantryman’s worst nightmare or best friend depending on where the shells are falling. This writeup seeks to introduce artillery to laymen.

Artillery I define as a crew-served weapon that is not man-portable and designed to destroy things that are hard to kill. Some types of artillery pieces may be carried by a team of men, others are not mobile at all in a practical sense. The purpose is to destroy targets at a distance. Usually gunners cannot see what they are shooting at. Nothing beats artillery for putting lots of ordinance on a target at low cost. Only aircraft bombs can do more damage, at much greater expense..

Artillery really began with the castle. Medieval fortification had developed to the point where thick stone walls were thick enough to shrug off any direct fire weapon such as a mangonel (what most people think of when they say catapult) and high enough to keep out weapons flung by a trebuchet. Armor had improved to the point where the best armor was all but impenetrable by any hand weapon. Gunpowder and metallurgy combined to fire heavy shells at sufficient velocity to batter down thick castle walls. Lighter guns, which still required emplacement could penetrate any armor. As castles and armor empowered the feudal class to resist their King, central governments and would be democrats embraced the gun as a more egalitarian weapon that could elevate common soldier. Guns also negated the ability of horsemen to snipe at soldiers from range with bows. Though guns of that period were inaccurate, unreliable and downright dangerous they outranged any bow.

There are three basic families of artillery.

Anti-tank artillery is designed to destroy tanks or other armored vehicles. Such weapons rely on kinetic energy to penetrate armor, or specialized warhead like a shaped charge. Anti-aircraft artillery is self-explanatory. Anti-aircraft guns fire at high velocities in order to get the shell to high altitudes, or rely on shooting many projectiles at low altitude to increase the probability of a hit. Space limitations prevent more than this brief mention here, except to say that many of the best anti-tank guns began life as anti-aircraft guns, the most famous being the German 88mm flak.

The third type of artillery is today’s subject: artillery designed to attack ground targets. This is the type of artillery most people think of. Most artillery pieces are guns of some form, but this category includes rockets and guided missiles.

In the early days all artillery pieces were guns. They came in three basic varieties. The mortar is a very short barreled gun that fires at a very high angle. Its primary use was to fire over, or into entrenched positions as an anti-personnel weapon. The shell does all the work, and muzzle velocities are very low.

Howitzers and cannon may fire directly at an object within their line-of-sight. Shells travel in a ballistic arc, a semi-elliptical flight path that allows for maximum range. In direct fire the weight and velocity of shot may be the primary killer. In a ballistic trajectory most momentum is spent getting the shell to the target, so the shell itself must become the killing force. Howitzers are shorter barreled, which reduces their range but makes them less expensive to build and operate as well as easier to transport for any given shell weight. Cannon have longer barrels. That allows the propellant charge more time to expand and thus forces the shell out at a much higher muzzle velocity. That makes the shells fly farther than from a howitzer, but the additional expansion wears the barrel and costs more to make. Range is very much a property of barrel length.

The ‘harder’ the object you seek to destroy, the larger the shot required. The larger the shot (and propellant charge) required, the bigger and heavier the gun, the greater the problem of recoil. There is always pressure to make guns get bigger and heavier (and thus more expensive). Increasing size and weight makes guns harder to emplace and operate. Manpower and supply problems multiply. The largest guns are often not mobile at all, but permanently emplaced. Others cannot be carried by less than a railroad car. Or an Iowa class battleship.

The larger the gun and charge, the greater the recoil. Guns prove Newton right: for every action there is an equal and opposite reaction. Early guns absorb recoil through their trail, the part that rests on the ground behind the gun. Many guns move when fired. Nineteenth century guns had a single trail, as do many direct fire weapons. But bigger guns that require higher elevation have split trails, where the trail spread out in a vee pattern and the gun can be elevated so the breech is almost within the tail structure. Weight of gun and shot and recoil very much limit mobility. One reason tank chassis are so popular for self-propelled weapons is because they were built for heavy loads.

As guns grew larger and more powerful simply relying on the trail no longer worked. Most guns today use hydraulic cylinders to absorb the recoil and return the gun to firing position. Tank guns often use a muzzle brake, a device the diverts some of the hot gasses. Recoilless guns really are not, but they seek to divert much of the blast, gaining a lightweight gun in return for striking power and range. As tanks grew tougher to beat anti-tank guns also grew. Thicker armor for heavy tanks like the German Tiger or British Matilda forced anti-tank guns onto vehicles because the needed guns became too big to manhandle. They also forced development of alternative warheads, such as the shaped charge.

Today most field artillery pieces have a barrel size between four and six inches (100 to 155mm). These shells weigh between 15 and 45kg, and can accurately strike targets up to 50km away. While monstrous guns firing fourteen inch shells were used in both world wars, such weapons are too big and slow firing for most uses. It's simply too hard to get them to where you need them, unless you put them on a ship. Monitors designed for shore bombardment also carried very large guns but were abandoned after World War II as insufficiently flexible.

Until the late 19th century most artillery pieces were muzzle loaders, with powder and shot rammed down the barrel from the business end of the gun. But in the late nineteenth century improvements in tooling and metallurgy made possible the development of breech-loading artillery. There are two types of gun used. A interrupted screw breech has a set of ‘teeth’ at geometric intervals on both the barrel and breech. An obdurator pad expands under pressure to seal the breach. Shell and propellant bags are inserted into the gun. The breech is then closed and rotated so the teeth interlock to absorb the explosion that takes place whenever the gun is fired. Screw blocks are less expensive, lighter and allow for more flexibility in shell and propellant. For example the shell and propellant can be separated and propellant charges adjusted as needed. This is the type of breech used in the largest guns and where a high rate of fire is not critical.

Sliding breech blocks use a large piece of steel which seals the breech and slides aside for reloading. This type of block is more expensive and can only fire shells that contain both shot and propellant in one body. They are preferred for situations where a high rate of fire might be necessary, such as tank and anti-aircraft guns. Breech blocks are used in guns up to six inches ( 155 millimeter ) as the breech block itself grows too heavy for practical use..

The introduction of modern breeches combined with new techniques of barrel casting in the late nineteenth century to bring about a revolution in artillery fire that became evident during the Franco-Prussian War of 1870. This is when artillery began to take its modern form. High quality optics and ranging techniques brought about a revolution in accuracy for World War II. Horsedrawn artillery was replaced by tractors, either wheeled or tracked. Indirect fire became more important than direct fire.

Guns excel at one thing, getting a lot of ordinance on target for relatively low cost. The guns may use high quality machining and advanced barrel-making techniques, but the ammunition is relatively inexpensive to manufacture. Cost is an important factor as ammunition shortages were felt by all combatants in World War II, particularly for the Germans.

The development of mobile armored forces during the Second World War created a serious stress in artillery design. Gunpower and range are often directly proportional to weight, but the bigger and heavier a gun gets the harder it is to move. That posed little problem for the relatively static battlefields of World War I, but with the Germans fighting wars of maneuver in the African Desert, France and the Eastern Front a problem quickly appeared in that the traditional towed artillery had an increasingly difficult time keeping up with the mobile forces they were intended to support. Ground attack aircraft and gunships are at heart airborne artillery, for they can put ordinance quickly wherever it is needed and quickly respond to changing conditions on the battlefield. But while such weapons serve a similar role and in many cases may even replace conventional artillery, airborne weapons are costly and not considered here.

Traditional towed artillery is relatively inexpensive, but takes time to emplace and disemplace, and often after firing it cannot catch up with the units they support. The solution was to mechanize parts of the artillery, using a tank chassis as the base for the self-propelled gun. The M7 Priest was based on the Sherman. The Germans built their Hummel on the PzKw IV chassis. Making the gun mobile increased the artillery’s ability to keep up and had the additional benefit of reducing its vulnerability to counter-battery fire via mobility and armor. Modern SPs are often mistaken for tanks.

Because artillery is an effective killer armies seek to ‘do unto others’ first if for no other reason than to minimze losses by your own side. An enemy whose guns work unmolested usually controls the battlefiled. Enemy artillery batteries become prime targets. The first problem is to find the offending guns. During World War II armies used ‘sound and flash’ system of finding other batteries. An observer at a known location would note the bearing of a gun flash and use the time interval between flash and noise to estimate distance. Bearing and distance gave you a chance. If two or more observers were able to get bearing then the enemy battery could be located with great accuracy.

The problem then becomes hitting the target. Artillery shells are affected by altitude, humidity, wind, temperature, state of bore wear, the angle of the ground the gun is sitting on, and the gun's relative elevation relative to the target. Barrel wear changes muzzle velocity which affects range enough that during World War II British gunners sought to calibrate their guns every third day. Hitting anything requires many computations and precise work. Indirect fire weapons are almost always located far behind the front for protection. That’s not usually a problem if all you want to do is support the troops. But enemy artillery is father back and so range becomes paramount. All things being equal, the longer the range of your guns the safer they are. Armies whose guns have limited range have to either expose them or use air power, which is far more expensive and risky. But effective counter-battery fire greatly increases the power of your own army by denying the enemy the protection of his own guns.

Today the issue has become even deadlier as counter-battery radars have supplanted the ‘sound and flash’ system. These radars are easy to use and give an accurate picture of the firing guns location , sometimes before the first shell lands. Of course that doesn’t mean the responding shell will arrive immediately. But in a contested environment today artillerymen preach shoot and scoot , the idea that you shoot at your target them move immediately. U.S. Army doctrine teaches units to move within three minutes of firing the first round. Counter-battery fire is expected within 3-5 minutes. Self-propelled guns enjoy a huge advantage here, even without protective armor.

Rockets represent one response to the problems of counter-battery fire. While a rocket is much more expensive than a conventional shell, the launchers are not. A modern cannon is a complex, precision made piece of equipment. A rocket launcher can be little more than a bunch of tubes welded together. Rocket launchers can be emplaced as quickly as an SP, they fire all their ordinance in seconds, and if destroyed the low cost makes them less of a loss.

But unguided rockets are far less accurate than artillery, which can be fired with exceptional precision. Unless given an expensive system of terminal guidance rockets have relied on sheer numbers and random luck to hit a target. Normally they’re used for suppressing an area. Because one launcher can fire many rockets within seconds, rockets do well at that kind of work. The shock effect of many warheads exploding at once is something gun designers have tried to simulate in an era where ballistic path can be planned by computer. But a gun can be targetted much closer to friendlies.

That ‘volley’ effect loses one of a gun's advantages, the ability to ‘walk’ a shell onto a target. Artillery fire can be adjusted, and thus used a lot closer to friendly troops than a rocket launch. Rolling barrages were tried in World War I but proved to hard to co-ordinate without good communication between the guns and the front. Armored vehicles permitted the Soviet tactic of opening a ‘lane’ inside a barrage for friendly assault troops to use. That sort of barrage requires a lot of guns, a lot of ammo and a great deal of skill, but the Russians used it with great success. The key problem becomes controlling the battery. Radio communication and moving observers close to the front greatly enhances the effectiveness of artillery.

Guided and ballistic missiles are usually considered part of the artillery. Space and time prevent more thorough coverage but missiles can be very precise and deliver ordinance a long way. Their downside is complexity and cost, such weapons are reserved only for very high value targets, particularly those who cannot practically be hit any other way. Sights have to be adjusted for individual guns and ammunition. Weather, inclination, barrel wear are all part of a good sight, and this before digital computers greatly simplified the process.

Artillery fire serves many purposes. It can be used to soften up enemy defenses for an attack. It can be used to keep heads down to cover movements, such as maneuver or withdrawals. On defense it can be used to destroy attackers and send them to ground, or to attack follow-on forces. Star-shells may illuminate a position, smoke may conceal it. If ammunition is plentiful, it may even be used for harassment and interdiction fire where short barrages are fired at irregular intervals at places of interest such as a road junction. Such fire is intended to keep the enemy insecure.

Indirect fire presents a special problem which is hitting a target the gunner cannot see. Accurate mapping is critical, and aerial photography represented a great advance. Civil War combatants initiated the use of balloons as observation platforms. On offence barrages could be pre-planned, but once battle began the ability to adjust fire was almost immediately lost. The defense could use telegraph wires provided they survived the attacker's preparatory bombardment, which rarely happened. Rockets or other emergency signals were used, and are still in use for emergency situations. Things changed during World War II. Radios made real fire adjustment possible. The Germans put artillery observers right up front which was an essential part of their blitzkreig tactics. But the greatest innovation came from the United States with the development of the Battalion Fire Direction Center. Lacking money for new guns in the period between wars, all American artillerymen could do was to figure out how to use what they had more effectively. The battalions on fire direction center controlled every gun in the unit in real tine even though individual batteries were dispersed. U.S. units began a set of targeting calculations the moment they began to emplace. A set was prepared for each of a detailed set of grid co-ordinates each battalions guns could reach. All guns were put under centralized control. Centralized control allowed accurate fire to be brought quickly with only map co-ordinates necessary. It also allowed for what became known as time-on-target fire where the guns of different batteries would all arrive on target at the same time. The U.S. army began putting experienced artillerymen in the front, and overhead in light aircraft. American artillery shocked even those German officers with experience on the Russian front. Today GPS has proven a great boon for artillerymen, who can zero their guns for firing much more quickly with the precise locations that system provides.

Another advance has been the development of specialized ammunition. The earliest shells were nothing more than solid shot. Later guns had an explosive filler with the explosion timed by adjusting the length of a cord fuse. Mechanical timers replaced the cords were used for airbursts, which place the explosion above ground for the greatest blast coverage. Later on radar based fuses entered service, particularly against aircraft. Mechanical igniters set off the charge on contact, or delays could be dialed in to penetrate beneath hardened targets such as bunkers. Shaped-charge and squash head warheads were developed to deal with hardened targets, and solid shot has not disappeared, it just got harder and heavier. More sophisticated ordinance appeared thanks to microelectronics. Laser guidance has been applied to artillery shells, and magnetic seekers have been created to hunt tanks. Other rounds disperse sub-munitions, either cluster bombs or small mines capable of crippling an armored vehicle. The sub-munitions themselves are becoming capable of independent targeting.

Artillery is organized primarily into batteries and battalions. Four or five guns with supporting vehicles make a up a gun battery. The guns are deployed 20-30 meters apart in an ideal world, and the trucks hidden somewhere else to reduce vulnerability to fire and observation. Three or four batteries make up a battalion. Battalions may be combined into regiments, but that's as big as pure artillery units get. Artillery is considered a separate branch in the miltary, equivalent to infantry and armor.

Today’s self-propelled cannon is a far cry from its renaissance era predecessor in every way, but the big guns still rule the battlefield.It is tellng that U.S. infantry doctrine stresses that a soldier's primary offensive weapon is his radio. While some have spoken of conventional artillery as obsolete it isn’t going anywhere. Whenever an army wants sustained indirect fire the guns will be there because nothing puts so much ordinance on target for less.