Ever since 1997, when General Charles C. Krulack, the Commandant of the US Marines, announced his directive regarding "Military Thinking and Decision Making", videogames have become an official part of the Marine's training arsenal. General Krulack's suggestion that "The use of technological innovations, such as personal computer-based wargames, provide[s] great potential for Marines to develop decision-making skills, particularly when live training time and opportunities are limited," outlines their importance. His insistence that "Imaginative combinations of physical and mental activities provide Marines [with] the opportunity to make decisions under conditions of physical stress and fatigue, thereby more closely approximating combat," clarifies how these games are to become a regimented part of an already rigorous training programme.

Indeed, it's clear from General Krulack's pronouncements that what he really wants is for his Marines to be thinking about war-fighting every day. His suggestion that, "Marines have always been innovators, and I am confident that creative ideas will be generated locally," has lead to the increasing prominence of the Marine Corps Modelling and Simulation Management Office (MCMSMO) and its PC-based wargames catalogue. It's also given thousands of Marines the chance to play videogames every day and call it work - they must be bloody delighted.

Based at Marine headquarters in Quantico, Virginia, MCMSMO's wargaming programme was kick-started by the actions of Sergeant Dan Snyder and 1st Lieutenant Scott Barnett, who noticed the potential of id Software's Doom games in relation to the basic operational fireteam unit of the Marines. As they put it, "We were playing Doom over lunch for a while [in 1995]... when we got the idea that it could be adapted."

And adapt it they did. The choice of Doom II was not an accidental one. id's shoot 'em up masterpiece supports four players simultaneously, and four players - fortunately enough - is the basic operational unit of the Marine fireteam: a lead officer, a machine gunner and two riflemen. Instead of the usual entertaining assortment of rockets, chain guns and BFG weapons of such hideous ferocity that all they leave behind them is a faint red mist and a vaguely uncomfortable feeling, Barnett and Snyder's Doom WAD includes the real deal. M-16s, M-249s and M-67 fragmentation grenades have all been accurately replicated within the game. These are serious weapons: take a hit and you die. There's no drama and no fantastic effects - it's all remarkably like the real thing, in fact.