America's Army is one of the most popular computer games on the planet and like many games, it is a shoot-em-up, get-the-bad guys kind of affair.
Novice players master everything from driving to basic first aid
But unlike other games, America's Army is truly a product of the US military. The Army first released the game a few years ago as a recruiting tool.
But, at the recent Serious Games Summit in Washington, DC, the Army showed off a new use for its computer game - training soldiers for combat.
America's Army now has six million registered users, and scores of fansites, worldwide. That is not just because the Army gives the game away online for free.
The action in this first-person shooter is often fast and furious, and in multi-player mode, you can play against more than a dozen other people.
But that kind of action comes only after a player has completed "virtual basic training," a game-based version of the real thing.
The novice America's Army player must master everything from firing standard military rifles, to learning basic first aid.
The game is also a crash course in what Chris Chambers, deputy director of the Army Games Project, calls "the core Army values of teamwork, integrity and leadership".
Mr Chambers also says that it quickly became clear that America's Army could be more than just a recruiting tool.
"We knew that this kind of technology is really good for small unit training. And its design is multi-player and internet distributed, so knew it could potentially serve a variety of distributed training needs, and that it could also interface with a variety of other existing Army simulations if we did some work."
During the past two years, the Army has been morphing America's Army into just such a training platform.
The wars in Afghanistan and Iraq have given the America's Army development teams real-life problems to tackle, such as how to protect convoys.
So, the Army has developed the Convoy Skills Engagement Trainer. The trainer strives to make the experience of convoy duty as realistic as possible. A real rifle sits mounted on a real gun turret, in front of three, wrap-around white screens.
The software, based on the America's Army game, projects a training programme on the screens. In this case, it is convoy duty in Baqubah, Iraq.
The action is shown on a wraparound screen
Your team's mission is to provide cover for a computer-generated vehicle ahead.
One soldier drives, while the other mans the weapon. The rifle's cartridge has been removed and replaced with a device that simulates real fire. A laser sight shows the shooter where to aim, as enemy forces pop out everywhere on the screens.
"You can even bring your own guns, your own vehicles to the training exercise," says Greg Owns, who is with Laser Shot, the company that worked with the US Army on the Convoy trainer.
"We strap a steering assembly onto your Humvee, and you're training with the rifles you carry, and the Humvee you got to the training site with. And I can make it look like a PC game, that the average 19, 20-year-old rifleman or combatant right now grew up playing."
The Army believes that the real power of this technology lies in the fact that it is multiplayer, and can be securely networked across the globe.
That would allow combat-hardened soldiers in the field to assist new trainees, according to the US Army's Chris Chambers.
"If we can distribute these things throughout units that are already forward deployed, we could potentially have soldiers in the field, where new enemy tactics are happening all the time, training with units back in the states that are awaiting deployment. It is a nice way to connect people."
Soldiers in the field could help new trainees
America's Army is not the Army's only gaming title.
Full Spectrum Warrior was developed separately by the US Army funded Institute for Creative Technologies at the University of Southern California.
The game was created specifically for Army training purposes, but is now available commercially.
Full Spectrum Warrior, too, is being used in projects designed to help soldiers in certain mission-critical areas, particularly in interpersonal skills.
"We're using the game to help train soldiers to deal with civilians, doctors, locals, priests and clerics, and town leaders," says the institute's Michael van Lent.
"It teaches them how to interact with those people, and how to negotiate with these people."
One physician at the institute is even using Full Spectrum Warrior to study post traumatic stress disorder in soldiers.
Mr Van Lent notes that these sorts of games will never completely replace live fire drills and gunnery sergeants.
But even the older generation of Army trainers are starting to see that hours of game play may be worth the time and money.
As one person involved with America's Army put it; "It is better that a soldier gets killed 1,000 times on a training device, than once in real life."
Clark Boyd is technology correspondent for The World, a BBC World Service and WGBH-Boston co-production