Turkey has finally signed the $2.5bn (£1.9bn) contract with Russia to buy S-400 advanced missile defense system. With a range of 400 kilometers (248 miles), the system can shoot down up to 80 targets simultaneously, aiming two missiles at each one, at an altitude of up to 30 km.

The system is not operationally compatible with the systems used by NATO countries, which gives Turkey a military capacity independent of the alliance. NATO commanders will not have control over it. The identification friend or foe (IFF) equipment won't prevent Turkey from using it against NATO aircraft and missiles. Reaching full operational capability will require Russian personnel to be stationed in Turkey on advice, assistance and training missions.

The technology transfer component of the S-400 deal is especially important as it would allow Turkey to rapidly expand domestic defense industry with Russia's help. Russia would supply two batteries and help Ankara build two more such systems. A few years ago, the US refused to let Turkey produce Patriot air defense systems on its soil and the deal was off.