The second pair of Patriot Missile batteries go live Tuesday as they set to defend Turkey from any possible attack from Syria.
A German official confirmed the missile batteries being sent by NATO countries are now operational.
The United States, Germany and the Netherlands each committed to sending two batteries and up to 400 soldiers to operate them after Ankara asked for help to bolster its air defences against a possible missile attack from Syria.
The frontier has become a flash-point in the 22-month insurgency against President Bashar al-Assad, with Syrian government shells frequently landing inside Turkish territory, drawing a response in kind from Ankara's military.
The two German batteries, which have been deployed around the Turkish city of Kahramanmaras some 100 km from the Syrian border, were in position and ready to use as of late Monday, the German security official said.
The first pair of batteries, sent by the Netherlands, went operational on Saturday around the city of Adana, southwest of Kahramanmaras.
The final U.S. Patriots are expected to arrive in Turkey on Wednesday and go active in the coming days. They are being stationed around three southeastern Turkish cities and NATO says they will protect 3.5 million Turks from missile attack.
Patriots are capable of shooting down hostile missiles in mid-air.