But under tight ROE of the sort often in place during modern wars, massive firepower can't be used. If an enemy is shooting at you - perhaps with a machine gun from a rooftop in a town - you often can't advance until the gun is knocked out. The machine-gunner will chop up your infantrymen before they can get close enough to hurt him. But you can't take him out because your normal means of doing so would flatten at least one building, quite likely killing bystanders unnecessarily and certainly upsetting the local population.
This is where the sniper comes into his own. The right high-powered rifle, in skilled hands, can match some machine guns for range. If not, snipers are experts at creeping up on people without being seen; this forms at least as much of their training as shooting does. A sneaky sniper team can very often clear away other obstacles too - ordinary troops with rifles or rockets in defensive positions, enemy snipers, pickup-truck mounted heavy weapons and so on. In a good position they can cover a large area with their long-ranging rifles, effectively dominating it and making it safe for friendly troops to move about in. As soon as an enemy shows himself, he is taken out - and no buildings get blown up, no bystanders get mown down.
Indeed, so useful has this sort of capability been in recent wars that demand for snipers has exceeded supply. The typical battalion sniper section, only able to furnish a handful of two-man teams, is insufficient.
This has led to widespread adoption in the US and British forces of the so-called "designated marksman" concept. These soldiers aren't full-on snipers, able to creep invisibly through miles of hostile country to within killing range of an enemy general or whatever. But they are good shots, and they have weapons with more range than a normal combat rifle.
In the US forces, the tendency is for designated marksmen to use old M-14 battle rifles with updated sights; British units mainly use the "Light Support Weapon" variant of their upgraded SA80s. In its intended role as a light machine gun the LSW was hugely unpopular, lacking the ammo capacity necessary to deliver the required firepower. However it does have the virtue of being very accurate when used in single-shot mode, as one would expect of the last product ever to come out of the old Enfield factory, and it makes a good marksman's weapon.
Meanwhile the snipers proper have moved on. In the early '90s there were two main options: an ordinary full-poke rifle cartridge on the lines of NATO 7.62x51 or Soviet 7.62x54R*, or the enormously more powerful and longer-ranging .50-inch/12.7mm calibre rounds originally developed for use in heavy machine guns.
At first there had been no rifles designed to shoot heavy cal-fifty ammo. One of the first snipers to use it, the legendary Carlos Hathcock of the US Marines**, made several very long-range kills in Vietnam using a specially modified heavy machine gun firing single shots and equipped with a telescopic sight.
Subsequently, somewhat more portable rifles have been designed to fire .50-cal rounds. Examples include the well-known Barrett, favoured for a time by the US special forces and the Provisional IRA. Some snipers prefer to use these weapons mainly for "anti-materiel" work - for instance, stopping vehicles by smashing the engine block.
Others, however, have employed the enormous potential range of the .50 in a normal anti-personnel role. The current distance sniping record is generally credited to Corporal Rob Furlong of the 3rd battalion, Princess Patricia's Canadian Light Infantry sniper section. In 2002, working in support of US soldiers in Afghanistan's Shah-i-Kot Valley, Furlong hit and killed an al-Qaeda machine gunner at a range of 2,430m - beating Carlos Hathcock's record by nearly 200m. Furlong used a MacMillan Tac-50 bolt action rifle.