Squad Basics
The general basis behind all infantry tactics is "leap-frog". Leap-frog is essentially where one unit lays down covering fire, that is shoots at the enemy in an attempt to scare or intimidate them, to allow for another unit to advance. As it is generally harder to shoot while moving than sitting still, and in general you are less exposed when laying prone and not moving than when on the run, one unit is tasked on protecting the other from enemy fire while that unit advances. In order to remain mobile and maneuver in to a more ideal location, soldiers rely upon covering fire, or suppressive fire, to suppress the enemy while the other teams moves in to position. This could be to move to cover or concealment, to flank the enemy, or general defensive purposes such as while one unit is reloading or performing some other action that stops them from being able to fire at the enemy. The general idea is to always have some soldiers shooting at the enemies, so long pauses don't occur in shooting where the enemy can rush out and take advantage of your defenselessness.

A trained soldier typically has little struggle hitting a still target out to 50-100 yards. With appropriate skill and time, hitting a paper target out to 50 yards requires very little skill. However, when that target is moving, and you are moving, and are being shot at, and ducking your head and you have just all of 2 seconds, if that to take your shot, accuracy goes down. From a 95% success rate to a .3% rate, combat accuracy is much lower than accuracy in training, as it's generally harder to hit the enemy when under stressful conditions. While quotes vary, and most ammunition is expended in training, it took around 50,000 bullets per enemy kill in Vietnam, and around 25,000 in WWII. While this is true of how many bullets is took per enemy kill, in combat it usually took between 300 and 3000 rounds. At incredibly close ranges, it generally takes between 3 and 20 rounds per kill, such as 3-60 feet, but it can still be difficult. It only takes one bullet to kill, however, and in the wrong conditions, a soldier can be killed by one bullet. Snipers for instance only use about 1.6 rounds per enemy kill, so it set up in the right situation, it possible to increase the kill ratio substantially. Infantry tactics revolve around being in a situation that allows for that kind of accuracy, while not being victim of an enemy that does this. While a machine gun can in theory mow down an entire squad of enemy units, most of the time this isn't the case. Plan A is always to kill the enemy with your first shot and only one bullet, but plan B is what to do if you don't. The basis of nearly all infantry tactics revolves around setting up for Plan A, and being ready for plan B. Plan A is to set up an ambush and shoot the enemy before they know you are there, but as anyone can attest to, most plans rarely survive first contact with the enemy.

So, what do you do if caught in a firefight? Plan A of course is to shoot the enemy. Plan B is to take cover and try to stay low. The lower you are to the ground, the generally harder you are to hit. You want to be as small a target as possible facing the enemy, so crouching or going prone is generally speaking the best way to avoid being hit. If you're only 10% of the size you normally are facing the enemy, they have 1/10th the chance of hitting you. You simultaneously want to look for cover, that is something that might stop a bullet. This may be a car, a brickwall, a concrete wall, a tree or a dirt hill, which is sufficiently thick to actually stop a bullet. It usually takes about 9 inches of dirt, 4 inches of concrete or 8 inches of wood to stop most bullets, but you usually want more than this and it varies bullet from bullet. Furthermore, you generally want to stop multiple bullets and bullets of all calibers, so 2 feet of dirt, 2 feet of wood and 8 inches of concrete is generally the standard. A car engine block or tires will usually stop most bullets used by infantry, that is between a 9mm and a .308, but car doors or thin pieces of the car likely won't. A flipped over table also won't stop a bullet unless it's more than a few inches thick, and a car engine won't explode because of the gasoline (at worst gasoline would leak out on the ground and catch on fire if the gas tank is pierced, since gasoline doesn't explode and bullets don't burn). In general you want to use your common sense and intuitively gauge what will and will not stop a bullet, which comes with experience, knowledge and training. The more of your body that is covered up, the harder time the enemy will have shooting you. If only your head peaks out over a wall for instance, then only your head is a target. Furthermore if you duck down behind the wall and only pop your head out for a few seconds, go back down, pop back out etc. the enemy won't know where you are, and thus will have an even harder time hitting you. Ideally you would have some kind of defensive barricade, such as sand bags or a concrete pill box designed specifically to stop bullets, but if you are on the move and can't carry this with you, local terrain, such as hills or trees will have to suffice. Since modern body armor has trouble stopping rifle rounds and the whole body isn't covered, in general it's best to assume that any bullet can kill you, and since body armor can only take so many rounds, you still don't want to pretend you are invincible on the battlefield. For the most part, you will be completely unprotected against enemy fire. Body armor is designed to stop shrapnel and pistol rounds, not full sized rifle rounds, so hiding is your best option for avoiding getting shot. Concealment has it's use, such as brush or a flipped over table. While it will hide you from the enemy view, it won't stop a bullet. While this is good in the short term, in the long term if the enemy discovers your position, it won't provide much protection as they can simply shoot in your direction so many times that the bullets would undeniably kill you.

While all cover provides concealment, not all concealment provides cover. Cover is something that will stop a bullet or explosive, where as concealment only hides you from the enemy's eyes. If you have no cover or concealment available, you can always make some. A well placed explosive can make a hole in the ground to hide in, or a much faster option is simply to drop a smoke grenade. Smoke grenades can be used to conceal your own position, which makes it hard to see you and thus hit you. If done correctly only your troops will be able to see through the smoke, but because of the difficulty of this it's generally assumed that smoke grenades work both ways, blotting out both yours and the enemy's vision (unless you have thermal vision cameras, in which case it's only the enemy's; unless they also have thermal vision cameras). Smoke grenades are used to give soldier's time to find cover or concealment, or to conceal their movements so their enemy doesn't know where you're moving. While an enemy will see the smoke and know that there are troops there, they won't know exactly when or where you will be, which gives you vital time to move to somewhere else.

Your strategy will be to progress to good cover and stay there until reinforcements arrive, artillery or aircraft bombard them or, until you are able to wipe out or deter the enemy attackers. What does one do if the enemy takes cover? If the enemy stays out in the open, simply fire at them and use all the firepower available to wipe them out as quickly as possible. The last thing you want is them to be able to get an angle on you, regroup or receive reinforcements themselves, so time is always a factor. Unless you have some ulterior objective, it's best to consume everything you have in a fight to win immediately. What does one do if the enemy takes cover? The five main ways to combat an enemy in cover, two that are only viable for infantry. When things break down in to "trench warfare", that is when both sides are in good cover and won't budge, there are certain methods to break this stagnating form of warfare and get an advantage over your enemies. The first one is simply to muscle through the enemy, to charge them and try to overpower them. This works well if the enemy is weak or you have good body armor, such as are in a tank, but if you don't have good body armor it usually means you will take heavy casualties. In the case of WWI for instance millions of soldiers were killed, and yet neither side ever gained more than 5 miles of ground. It's a strategy that generally isn't very effective. The second strategy is to tunnel under the enemy but given the amount of time and effort it takes, the enemy usually can see it coming, and in general you simply cannot execute the strategy in combat (it was also true that it didn't work in WWI). The third strategy is to go over the enemy, but unless you're an airplane or can otherwise fly, this also isn't a possibility. The fourth and fifth strategies are the one's that actually work for infantry, and this is indirect fire and flanking. Flanking is where a group of your men moves over to attack the enemy from another angle. While one team lays down suppressive fire and the other moves to flank the enemy, you can use leap frog to allow for a unit to progress to a position where they can attack the enemy. If by yourself, you can lay down covering fire and move at the same time, but it will be much harder. The other option is indirect fire, say artillery bombardment, a grenade or grenade launcher. The idea is to shoot over the enemy and then have an area-of-effect weapon, like a grenade, take out a bunch of enemy's behind cover. In this way, you engage the enemy beyond their cover, and without having to move your position. If you can call in mortar fire, artillery or an air strike, this is also a viable option. Much of infantry tactics revolves around finding and pinning down the enemy, and then bombing them from a distance. When this isn't available grenades, grenade launchers or flanking the enemy are generally the preferred method. When maneuvering closer to allow for the use of grenades or maneuvering to a flanking position, leap frog is required.

Leap frogging should not be done for it's own sake, however. Whenever you are in a good position, you should simply stop. When in that position, it's best to take advantage of superior cover and the firepower that affords you. Defense, in combat, is generally the biggest force multiplier. If you can shoot at the enemy and kill them but they can't shoot at you and kill you, you generally are far more likely to win. In the Alamo for instance, a handful of men in a good position managed to kill 5 times as many men as their own, merely due to good positioning. In any defensive position, a handful of men can often take down a bunch of men, hiding behind cover and firing at the enemy, such as in a castle. History has shown that good defenses are often the best offense, and the biggest force multiplier available. Infantry tactics revolve around trying to produce force multipliers, the biggest of which is terrain. Be it in the battle of Thermopylae with the Spartans, or D-Day, nothing but terrain often allows for

Fire and Maneuver Team
Fire and maneuver teams are the smallest possible set-up one can have. It usually consists of either 2 soldiers, 1 soldier providing covering fire and the other advancing in alternating positions, or 2 groups of 2, doing the same thing. While this is usually only done when taking heavy casualties, in small units such as engineer teams or reconnaissance teams, or by police, it can be done professionally as well. LRRP teams or long range reconnaissance units, such as those in the rangers or marines, often times move in fire-and-maneuver teams, allowing for the smallest possible unit with strategies available.

Fireteam

Squad

Platoon

Company