The sniper is without doubt the most feared combatant in any theater of war, the best of whom have an array of skills far beyond simply being able to hit human targets at a distance. Snipers are the most cost effective way of killing the enemy.

Individual snipers routinely account for more kills than entire battalions operating in the same place at the same time, hit the target almost every time, and each bullet costs around €2.

What's more, snipers inflict a psychological terror on an enemy force that restricts its ability to operate effectively – when elite snipers are operating, they are invisible close up, and can strike from enormous distance, so nowhere is safe.

Indeed, an elite sniper's skills cannot be assessed with a single measurement, so the “longest confirmed kill” record stands as the pseudo world championship for military combat riflemen, and as of now there's a new outright champion - using an Accuracy International L115A3, British Corporal Craig Harrison killed two Taliban with consecutive shots at a distance of 2.47 kilometres (8120 ft) in Helmand Province, Afghanistan last November (2009). He then fired a third shot and hit the Taliban's PKM machinegun in perhaps the most prodigious feat of marksmanship in military history.

If you're wondering why it took so long for Harrison's kill to be made public, (it was made last November and only became commonly known in the last few days), understand that the publicity such a feat brings may not necessarily be wanted, or healthy, particularly if you are still "in theater". Harrison, who also survived a bullet passing through his helmet, and two broken arms from an IED explosion, has now finished his tour of duty and the story can be told.

The previous longest kill by Canadian Army Corporal Rob Furlong had been spoken of by soldiers in hushed tones for five years before it fell upon the ears of a reporter and become public knowledge and his name revealed.

Harrison's feat is clearly the stuff of legend.

The previous record holder - Furlong - killed an al-Qaeda fighter from 2.43 km during Operation Anaconda in Afghanistan in 2002. Furlong's shot was also legendary – he made military history. There would not be any military personnel in the world who would not be aware of Furlong's feat, and subsequently Harrison's, and who would not measure that distance off towards the horizon every day when they are in a combat zone.

Harrison bested it TWICE – with consecutive shots – then fired at and hit the much smaller target of the gun the Taliban had been carrying. This is completely without parallel in military history.

The rifle used by Furlong for his previous record was the “Big Mac”, the McMillan Bros Tac-50 used by Canadian Special Forces and the best .50 sniper rifle in the world.

Like Juan Manuel Fangio's car, Valentino Rossi's motorcycle or Sir Donald Bradman's bat, a varying proportion of the glory should also go to the champion's tool of choice – for snipers, the tool of choice is critical, with Harrison using an Accuracy International L115A3 Long-Range rifle – a rifle originally developed by an Olympic gold medalist target shooter which we wrote up two years ago in an article entitled – the best sniper rifle in the world.

Craig Harrison's AI L115A3 cost the British Ministry of Defence GBP23,000 (US$34,000), weighs 6.8 kilograms, and fires an 8.59mm bullet which is heavier than the 7.62mm round of the previous L96 model and hence less likely to be deflected over extremely long ranges. The L115A3 has a five-round magazine, enabling the sniper to fire five rounds rapidly, though that would almost never happen.

The L115A3 has an adjustable cheek piece to comfortably align the shooter's eye with scope, and a folding stock so the rifle can be more easily carried in a backpack.

It comes with an adjustable bi-pod stand and a suppressor to reduce the flash and noise of the gun – once the enemy knows where a sniper is, he too becomes a target – and a scope, in this case a 25 X magnification S&B 5-25x56 day scope.

In extremely skilled hands, the L115A3 can hit a human-sized target from 1400 meters (even at that range, it hits harder than a .44 Magnum does in the same room), which means Harrison's shots put him in almost superhuman company, as he almost doubled that distance, in combat, and killed a first then second Taliban with consecutive shots, then took a third shot at the PKM machinegun they unfortunate pair had been carrying with the intention of disabling it – the gun was hit but damage could not be assessed.

Firing one bullet with that accuracy over more than a mile and half, has never been recorded previously – Harrison did it three times running. Though the bullet leaves the barrel at three times the speed of sound, it still takes more than two and a half seconds to travel that distance. Though the day was clear and still and in thin mountain air, Harrison still had to aim six feet higher than the targets, and two feet to the left to allow for the gentlest of breezes and bullet fall.

While Harrison's feat is perhaps the most prodigious in the history of military marksmanship, the most common way of assessing the effectiveness of a sniper is the number of "kills" and by that measure, Finland's Simo Häyhä was the most deadly sniper in history.

During just 100 days of the Winter War (1939–1940), between Finland and the Soviet Union, Häyhä was credited with 505 confirmed kills of Soviet soldiers - that's five a day. He worked in white camouflage in temperatures between −40 and −20 degrees Celsius, and amassed the greatest sniper tally in history.

Besides his sniper kills he was credited with 200 from a Suomi KP/31 Submachine gun, topping off his total confirmed kills at 705.

If the world of the military sniper is intriguing to you, I can suggest an excellent new book on the subject written by Hans Halberstadt entitled “Trigger Men” I just spent seven and a half hours listening to the audio book though, go figure, exactly the same book is much cheaper in printed form, despite the cost of paper and printing and binding and schlepping and postage.

The book more than adequately kept my brain busy during an international flight and covers the exploits of the modern sniper with hours of anecdotes from Iraq and other recent wars. Halberstadt spoke with some of the most revered names in sniping history to put the book together – names such as Carlos Hathcock II, who recorded 93 kills, including one of 2.29 kilometers during the Vietnam war, and Sgt James Gilliland, who also pulled off one of the most remarkable kill shots ever recorded in a strong breeze. The role of the sniper has changed, and this book explains why.