The S-400 Triumph (NATO reporting name: SA-21 Growler) is an air defence missile system developed by Almaz Central Design Bureau of Russia. The new system replaced the S-300P and S-200 air defence systems of the Russian Army.
The S-400 was developed as an upgrade of the S-300 series of surface-to-air missile systems. The system entered service in April 2007 and the first S-400 was deployed in combat in August 2007. Russia set up four S-400 regiments defending national airspace in the Moscow region, the Baltic exclave of Kaliningrad, and the Eastern Military District.
The air defence units of Southern Military District are expected to be rearmed with advanced S-400 Triumph by the end of 2012. Over 20 battalions of S-400 Triumph will be delivered to the Russian armed forces by 2015. Russia plans to induct 56 S-400 battalions by 2020. Russia intends to supply export versions of the S-400 Triumph system to the armed forces of China. Turkey also expressed interest in purchasing S-400 air defence systems during the IDEF 2009 exhibition.