A shoulder-launched missile weapon is a weapon that fires a projectile at a target, yet is small enough to be carried by a single person, and fired while held on one's shoulder. "Missile" is used here in the original broad sense: today the word has a strong connotation with the concept of a guided rocket. There are two kinds of shoulder launched weapons. The first is the recoilless gun, which is essentially an open tube. When fired the reaction gases (with a momentum equal to the projectile) expelled out of the back of the weapon compensate the force exerted on the projectile. The other type uses rocket propelled projectiles; these typically also use a small recoilless charge to get the projectile out of the barrel and to a distance where the operator will not be hurt by the rocket's backblast; when the rocket ignites at a safe distance, it further accelerates the projectile or at least keeps it from decelerating in its trajectory.
The smallest shoulder-launched rocket weapons are rocket-propelled grenades (RPG). There are also larger "dumb" shoulder-launched missiles, used in a similar way to an RPG, but with far greater destructive power. A number of specialised "smart" missiles are available in shoulder-launched forms, including (anti-tank guided missile) and man-portable air-defense systems (MANPADs), surface-to-air missiles used as anti-aircraft, typically using infrared homing and used to target helicopters and other low-flying aircraft.
Shoulder-launched rockets have a launch tube. In order to prevent the user from being burned by the exhaust, the rocket (or at least its first stage) must burn out before it leaves the tube, and if present the second stage must fire once the rocket is well clear of the launcher. Even if the operator is safe, there is a sizeable blast effect to their rear.
Also, the rocket must have a reliable ignition system. In modern systems, this is almost always a percussion cap. This system was not fully developed until the German Panzerfaust of World War II, an early one-shot design that however also was the first practical recoilless antitank-gun and thus used no rocket. The bazooka and Panzerschreck were later rocket-propelled developments which could be reloaded.
From their first inception during the Second World War, many portable missiles have been used to give infantry a weapon effective against armored vehicles and fortified structures. The power of the shaped charge meant that the effectiveness of the weapon was not limited by a gun barrel bore nor size of weapon as for example a conventional armor piercing shell from an artillery piece. As such these manportable weapons could be used to equip infantry units with their own anti-tank and anti-aircraft weapons.
Shoulder-launched rockets or recoilless guns are a favored anti-technical weapon. They permit otherwise lightly or poorly armed troops (eg militias) to destroy modern sophisticated equipment such as close air-support aircraft, helicopters, and lightly armored vehicles.
Attacks come from ambush for the element of surprise and attempt to immobilize a convoy of vehicles, then destroy its defenders, then destroy its contents, then escape before air or artillery support can arrive.
Normally, the militia will plan to have two to four shooters per attacked vehicle. Reliable attack ranges are 50 to 100 m, although attacks can succeed out to 300 m. Self destruct ranges of common rocket weapons such as RPG-7s are about 900 m.
The usual response to such attacks is to suppress the shooters, with saturation anti-personnel fire, artillery or aerial barrages in area-denial attacks. Submunition and thermobaric weapons are often used to clear landing zones (LZ) for helicopters.
In modern anti-insurgent operations in misty, dusty or night-time situations, advanced optics, such as infrared telescopes, permit helicopter gunships to surveil convoys from beyond human-visible range, and still attack insurgents with inexpensive anti-personnel fire. This approach is more economical than area-denial. Protecting as little as 20% of the convoys rapidly depletes an area of active insurgents.