The American armed forces have gotten into computer games in a big way. This is nothing new, but it's gotten really huge with the development of more realistic, and easier to use, game development technology over the last decade. Since the 1970s, civilian wargames have been adapted to military use. These earlier games were time consuming to learn, and use. That changed as computer games arrived, and the technology that powered them developed. This became pretty obvious over the last few years.
For example, "America's Army," a multi-player online game, appeared in 2002. Since then, over six million users have joined the game, and over 50 million hours have been spent playing what is, essentially, a recruiting pitch for those interested in joining the U.S. Army. But most of the military computer games are not made available to civilians, but are used internally for training. Not just combat training, but increasingly for non-combat training as well.
While civilian developers (the same ones who work on stuff you can buy in a store) have been used to create most military games, increasingly, uniformed personnel, or civilian employees of the Department of Defense, are creating the games. Many tools and game engines are available for anyone to buy if they want to develop a new game. Many commercial games take this approach, spending over a million dollars for the "off the shelf" game engine, graphic elements and special tools, used to create a new title. A game engine is basically the guts of an existing game (usually a very popular one), with all the graphic and story elements stripped away. The publisher who developed the original game can then recoup some of the development expense by leasing the game engine to other publishers in order to do different (but, obviously, somewhat similar) games. Other bits of software, especially graphics, can be bought, modified, and inserted into a new game, at a fraction of the cost of creating stuff from scratch.
The military has gotten used to these tools and techniques, and has another advantage in that many of their games do not have to be as snazzy (heavy on the eye candy) as commercial games. This is especially true for computer games dealing with combat support jobs. Since these tasks occupy over 90 percent of the people in the military, this has become the fastest growing segment of the military computer games activity.