ARMA 3 is an open-world military tactical shooter video game developed by Bohemia Interactive for Microsoft Windows. It was released on September 12, 2013. ARMA 3's storyline takes place in the mid-2030s during the fictional Operation Magnitude, a military operation launched by NATO forces fighting in Europe against "Eastern armies" referred to as CSAT (Canton-Protocol Strategic Alliance Treaty) led by a resurgent Iranwith a coalition of other Middle Eastern and Asian nations.