Military cover shooters have become a genre onto themselves in recent years, thanks to the success of franchises like Call of Duty and Battlefield. Gameplay in these titles focuses on tactical teamwork and army culture, turning away from the more fantastical elements of modern action gaming in both story and implementation. Insurgents sit in for aliens and narratives spring from newspapers instead of novels, all in the service of "realism." Realism means different things to different people, however, and hardcore players have long wished for a game that combines a multiplayer military tactical approach with the level of detail seen in proper simulations. Czech developers Bohemia Interactive have been dabbling in this field for almost a decade following the debut success of Operation Flashpoint, and ARMA II: Combined Operations ($33, free demo) is their most recent marketplace deployment.

Combined Operations bundles several releases under a single title, including ARMA II and the standalone Operation Arrowhead expansion. That translates to a lot of mission for your money, but keep in mind some of the content shipped in 2009 when ARMA II was initially released. The gameplay found here is of a specific flavor and the difficulty level an order of magnitude more challenging than a traditional FPS. Not all of that challenge is due to the gameplay, either. There's a general imprecision to the controls and sluggishness to movement that pervades Bohemia's 3D engine and makes game interactions feel like your computer suddenly skipped two upgrade cycles. Other game mechanics are equally poorly implemented. Climbing ladders, utilizing inventory, and operating vehicles are all examples of obscurely designed mechanics that feel more like add-ons than actual core code.

To counter this, Bohemia offers a sandbox experience par excellence, with mission design tools and an easily moddable structure that invites users to take chances and play around with the results. This more than anything has been the key to ARMA's success. For example, you might ask why this elderly niche shooter leads the sales charts at Steam so frequently, but the answer is simple: This is the package that's required to run DayZ . Forward thinking and trust in their community paid off to the tune of 1.3 million new sales and development of what's sure to be a hit sequel, largely without Bohemia lifting a finger to do anything other than count all the money. I wonder if encrypted game files still seem attractive to their competitors.

Most of ARMA II's real action takes place in multiplayer mode, where cooperative teams can employ small unit tactics and other military strategies against one another. The levels are vast–hundreds of kilometers in size–and the game's architecture supports dozens of players, vehicles, and aircraft simultaneously so aerial support, heavy weapons coverage and more are all part of the tour. Weather changes, terrain, and day/night cycles are all crucial tactically, while enemy AI is good enough to be uncanny at times. The promise of all this is tempered by the reality of the engine's shortcomings, but it's an impressive feat nevertheless.

Performance doesn't scale well with system requirements. Most desktop gaming systems beyond minimum spec will be able to provide good framerates with some high end effects enabled, but running on ultra requires top end hardware and won't return particularly stunning visuals. The laptop experience is iffy. Easy maps on low settings pass for playable on mid-range mobile gaming systems, but elaborate maps and more demanding settings turn assaults into powerpoint presentations. Chances are your laptop won't cut it.

With ARMA III on the horizon, Combined Operations is difficult to recommend. Hardcore players may be drawn to the high levels of detail and realism, but they are sure to find disappointment in some of the awkward systems that lay underneath the uniform. For these users, I'd recommend waiting for a sale at Steam or GOG before taking the plunge. Players curious about DayZ shouldn't wait however. ARMA's flaws aren't nearly as disruptive in that environment, and the excitement around the mod makes playing sooner rather than later worthwhile.

Note: The "Try it for free" button on the Product Information page takes you to the vendor's site, where you can download the latest version of the software from the vendor of your choice.