February 25, 2011: Russia has deployed its second and third S-400 anti-aircraft missile battalions. One battalion went to the far east, the other to Moscow. A year ago, Russia activated its first S-400 (also known as the S-300PMU-3, SA-21 or Triumf) battalion, around Moscow.

This new version of the S-300 pays particular attention to electronic countermeasures that the Americans might have, or be developing. The missiles are also physically larger and have longer range. Three years ago, Russia announced that the first S-400 had entered service around Moscow. But that didn't actually happen, and development work continued until test firings of the missiles were successful. Each S-400 battalion has eight launchers, each with two missiles, plus a control center and radar.

The S-400 is similar to the U.S. Patriot, and is expensive. Russia is now offering to export the S-400, despite all the advanced technology in it. Meanwhile, work is underway on the S-500, which is scheduled for deployment within four years. The S-400 missiles weigh 1.8 tons each and are 8.4 meters (26 feet) long and about 50cm (20 inches) in diameter. The missiles have a range of some 400 kilometers, and can hit targets as high as 100,000 feet. The missile has a 145.5 kg (320 pound) warhead. The target acquisition radar has a range of 700 kilometers.

The S-400 has over five times the range of the U.S. Patriot, weighs twice as much and claims the ability to detect stealthy aircraft. The S-400 also has an anti-missile capability, which is limited to shorter range (3,500 kilometers) ballistic missiles. That would mean a warhead coming in at about 5,000 meters a second (the longer the range of a ballistic missile, the higher its re-entry speed.)

The S-400 system actually has two types of missiles, one of them being a smaller, with a shorter range (120 kilometers). These are deployed four to a launcher, like all other S-300 systems. The S-400 has no combat experience, but U.S. intelligence believes that the tests these systems have undergone indicate it is a capable air defense weapon. Just how capable won't be known until it actually gets used in combat.

Russia plans to buy up to 200 launchers (each with two or four missiles) by 2015, and phase out the older S-300 and S-200 systems. This would mean deploying at least 18 battalions in the next six years, and perhaps more than twenty. The S-400 is sometimes described as an improved version of the S-300. Basically, it is. This is how Russia prefers to develop weapons, making incremental improvements on a basic design, and doing so for decades if the system continues to be successful.

Russia currently has about 160 S-300 battalions, but about a third of them (the older models) are in storage.