An armored personnel carrier (APC) is a vehicle designed to carry soldiers, weapons and equipment around the battlefield and to provide limited protection against weapons common to that battlefield. They are war's 'battlefield taxis" and are designed to move people about when the going gets rough. They come in all shapes and sizes and fill a multitude of roles. Heavily armed versions known as infantry fighting vehicles have turned APCs into mini-tanks. This writeup introduces their long history and development.

The true history of the modern armored vehicle begins during the First World War. The realities of trench warfare came as a rude shock to officers in World War I. Machine guns, barbed wire and trenches gave overwhelming superiority to the defense. The simple fact was men could not take a defended position without enduring hideous casualties, despite incredible artillery preparations from thousands of guns. In fact the artillery barrages proved part of the problem, they tore up the earth all around the battlefield, making it all but impossible to cross.

World War I came as a surprise in other ways. The cavalry had been the pride of the army, but the horse soldiers performed poorly in modern combat. The problems continued outside of direct combat. Horse-drawn and foot transport really wasn't good enough in the modern world. Armies didn't exactly get rid of the horse (in fact most German transport was horse-drawn at the beginning of Word War II) but horses were extremely vulnerable to fire, and the mud characteristic of trench warfare slowed them down a lot and stripped them of much of their load carrying capabilities. Men were better in mud, but not much, and could not march quickly enough. The imperatives of battle were such that soldiers had to be able to move in almost all conditions, and if breakthroughs were to be exploited, they had to move fast.

The ultimate solution reached was the tank. The track laying system could get soldiers across very rough and soft terrain, and armor protected them from most weapons. However tanks have their limitations. You can't see out of one very well without sticking your head out to be shot at, something most tankers don't do in heavy combat. A smart infantryman can easily sneak up on a lone tank, and if equipped with the right anti-tank weapon, put it out of action. So the most effective way to use tanks is with infantry, who can see quite well but aren't terribly resistant to artillery and gunfire.

The British realized this and in 1917 developed the first armored personnel carrier the Mark IX, essentially a redesigned and lengthened version of the Mark V Male tank of the period. The idea was to protect the infantrymen from machine gun fire until they got across the battlefield, when they could dismount and serve as the eyes and ears for the tanks. Because military operations rarely take place where paved roads are ubiquitous, it was realized that infantry would have to be mechanized in vehicles capable of crossing poor, undeveloped or no roads at all. The next generation of armored personnel carriers were half-tracks. Vehicles like the German SdKfz 251 and the US M3 halftrack served as the prime movers near the front during World War II. They steered like cars with the track system designed to provide traction under conditions of mud and snow. The vehicles were lightly armored (primarily against small arms) and usually equipped with a machine gun for air defense. Some were used to mount heavy mortars or to tow artillery to give the big guns the ability to keep up with the tanks.

These halftracks, like most APCs, provided fairly roomy armored hulls and load-carrying capability. Much military equipment is heavy, and if it is to keep up with the tanks it has to be mechanized. From the beginning APCs have been adapated to many roles, and come in many specialized variants. Room to spread out a map and operate many radios made them prime candidates for command vehicles. Specialized mortar and anti-aircraft vehicles abound. Troops need to be resupplied in combat and so they often serve as trucks where shooting is expected. There are electronic and fire control variants. There are about a dozen specialized standardized variants of the American M113, and that's not atypical.

The second problem was artillery fire, as guns had made quantum leaps in numbers, firepower and accuracy during the first half of the 20th century. Longer range guns could reach deep behind the lines to strike second echelon forces. During the war soldiers began to realize that the best time to attack an enemy combat force came before the enemy deployed for combat. Cold War doctrine for the U.S. Army stressed attacking Warsaw Pact units well behind the lines, as they were easier to hurt, and it was discovered such hits could produce predictable times of weakness that could be exploited.

This thinking drove the APC to its current form. An oustanding example that came from that period was the US M113. Essentially a box on tracks, it is armored to resist light machine gun fire (heavy machine guns from the front) and light artillery fragments. NATO officers have always respected the power and numbers of Soviet artillery. APCs are designed to survive near misses from artillery and keep their passengers safe from snipers until deployed. APCs are not armored to resist direct hits from heavy weapons, That much armor would render them too heavy and immobile. (The Israeli Achzarit is a notable exception, formed out of captured T-55 tanks and Israel's historic manpower shortages.) The sides tend to be lightly sloped and with heavy sloping on the front where more protection is often needed. Many APCs are amphibious to get across the many waterways found in the field, but most are poor swimmers requiring ideal conditions to cross. Most APCs are lightly armed - usually just a machine gun.

This "box on tracks" form is not ubiquitous. Nor are tracks mandatory. There have always been armored cars, but recent advances in wheeled technology have produced mobility very close to tracked vehicles, but without the enormous maintenance and other costs associated with tracks. Plus they don't need transporters for long moves. The price for this is armor, because little can be carried. Second, not all APCs are boxes. In Vietnam U.S. troops often rode on top of their M-113s because they were more afraid of RPGs and mines than artillery or gunfire. In the 70s South Africa noticed their Angolan and African National Congress opponents didn't have much artillery but they did have mines, so they designed the open topped and very odd-looking buffel to protect against them. APCs are often used in reconnaissance because their armor can protect them against the odd rifleman while searching for the bad guys.

The Russians took the next step and brought us the first infantry fighting vehicle (IFV). Their tactics drew on World War II experience and stressed offensive operations. Experience taught them to try and get through any breakthrough as quickly as possible to prepare for counterattack. The idea was to create a breakthrough so ideally you'd have to carry infantry past the front to exploit any opportunites. They also recognized the growing number of anti-tank weapons on the battlefield, and soldiers do not enjoy just hunkering down under fire, they like to shoot back. They figured that if an APC had to cross a battlefield it might as well be able to fight. The BMP-1 was the world's first infantry fighting vehicle. Armed with a turreted 73mm gun, Sagger anti-tank missiles and machine guns it was intended to pin down enemy soldiers while on the attack, and to support infantry with heavy weapons after they dismount. Heavy machine guns, cannon and anti-tank weapons are very heavy, often too heavy to be carried. Moving them onto the APC was seen as a way of giving the infantry more firepower and mobility. The IFV minimizes the historical fact that many military hybrids don't work very well, but IFVs do give a motorized unit a lot more firepower. History shows that if commanders have an armored vehicle available, they'll use it regardless of its intended purpose. In Vietnam, lightly armored M-113 APCs were often used in the assault role because tanks weren't available. At least the IFV carries enough firepower to breach many prepared positions.

Western soldiers looked at the new BMP and had a collective moment. They did notice that the IFV was packed with ammo which might go boom if hit with the right weapon, but it was also fast and low and most soldiers don't aim too well when they're being shot at. They also had another moment when they started counting Soviet tanks, all of whom are fast, low and well-shaped. Defeating armor in such numbers seemed a daunting process, and the profusion of Soviet APCs simply multiplied the problem. They knew they'd never get enough tanks to match up. So NATO commanders tried to saturate the battlefield with their own anti-tank weapons, particularly promising guided missiles like the TOW. However, guided anti-tank missiles come with their own set of issues. Most move rather slowly with the flight time counted with seconds and most produce a fairly distinctive back-blast that can be targetted. Since aim must be maintained during the entire flight it was decided to put the weapon (and others of its type) under armor in hopes that the gunner will take heart and keep his eye on the target. Given that NATO troops expected to fight on the defensive from prepared firing positions, the IFV might very well survive long enough to bring its weapons to bear.

NATO adapted many standard APCs yet the BMP inspired plenty of western imitators. The M2 Bradley was designed primarily to bust BMPs. To fight tanks designers gave it a TOW and put the operator under armor. The 25mm Bushmaster was intended to slice up more lightly armored vehicles like the BMP. When moving across the battlefield the crew was supposed to use socketed mini-M16s to keep enemy infantry off their back (the M231 firing port weapon). The M231 can't be aimed and hitting anything while racing across country is a very dim prospect. But you can bet the mounted infantry will use them just to keep busy and at first they'll keep enemy infantry down too. Like the BMP in combat it is supposed to operate behind its deployed infantry and bring heavy weapons to bear. And it's fairly heavily armored by APC standards. Reactive armor can make them rather RPG resistant, but dismounted infantry will want to keep a safe distance away from the competing blasts.

Armored personnel carriers are not going away. They can cross most terrain and protect their passengers against most threats. They can carry heavy stuff where needed and fill just about every role. And they're armored, and most soldiers believe you can't have too much armor around, so long as it's far enough away not to bring a bomb down on the nearby infantry. The combination of mobility, flexibility and armor is more than enough to keep around for the foreseeable future.

IFVs are also known as armored fighting vehicles or AFVs, the choice being personal preference.