ArmA: Armed Assault (known as ArmA: Combat Operations in North America) is a tactical military first- and third-person shooter which was developed by a 40 member team at Bohemia Interactive (BI), an independent game developer based in the Czech Republic.
ArmA is the spiritual successor to Operation Flashpoint: Cold War Crisis and features an overhauled game engine, with improved graphics, physics, multiplayer functionality, scripting capabilities, and new units and vehicles. An expansion pack titled ArmA: Queen's Gambit was released in 2007.
Source: Wikipedia, "Armed Assault", available under the CC-BY-SA License.