Producer: Almaz-Antey, Russia's largest defense contractor.
NATO Reporting Name: SA-21 Growler
Purpose: To deter foreign air and missile attacks on large population centers, military bases and sensitive research facilities.
Armaments: According to a recent report by the U.S.-based Center for Strategic and International studies, the S-400 system employes three types of surface to air missiles tailored to engage targets at various ranges: The 40N6 very long-range missile, which is capable of hitting a plane 400 kilometers away; the 48N6 missile, with a maximum range of 250 kilometers, and the 9M96 missile, which is used to destroy enemy aircraft under 120 kilometers away.
Developed: Work began on the S-400 system in the 1990s, and testing began at the Kapustin Yar test range in Astrakhan in 1999. However, delays in its development prevented the S-400 from entering service with the Russian military until 2007.
Capabilities: The system can effectively engage up to 36 targets within a 400 kilometer range with up to 72 missiles as once, according to the South China Morning Post. The S-400 also has some anti-ballistic missile capabilities, though they are less capable than the S-500 missile system, which is coming up in 2016, according to news reports.
Components: An S-400 division consists of eight surface-to-air missile launchers, each equipped with 32 missiles, as well as a mobile command center and radar stations. The makeup of the division can be tailored to fit the needs of the end user with various types of radar and various support vehicles. In short, an S-400 unit is a group of vehicles and equipment that work together to create a powerful air-defense system.