Minimum:

OS: OSX 10.8
Processor: Intel Core 2 Duo T7700 2.4 GHz
Memory: 2 GB RAM
Graphics: ATI Radeon HD 2600 PRO with 256 MB VRAM or nVidia equivalent
Network: Broadband Internet connection
Storage: 800 MB available space
Sound Card:
Additional Notes: iMac (Mid 2007 or newer), MacBook (Late 2008 Aluminum, or Early 2009 or newer), MacBook Pro (Mid/Late 2007 or newer), MacBook Air (Late 2008 or newer), Mac mini (Early 2009 or newer), Mac Pro (Early 2008 or newer), Xserve (Early 2009)

Arma: Cold War Assault Mac/Linux screenshots