Russia’s chief of staff made a surprise visit to Ankara on Friday during which he held talks with his Turkish counterpart, local media reported. Russian Chief of Staff Valery Gerasimov and his Turkish counterpart Hulusi Akar focused during their discussions on Friday on the situation in Syria and Iraq and the necessary measures needed to combat terror organizations, said a statement from the Turkish military. The meeting was preceded by talks Akar held on Thursday with his Iraqi counterpart Othman al-Ghanimi, US European Command Command Curtis Scaparrotti and US Central Command Commander Joseph Votel on regional security and counter-terrorism. Turkish sources said that Akar and Gerasimov’s talks also addressed the S-400 missile system agreement signed between Ankara and Moscow. Turkey has repeatedly criticized NATO for failing to provide it with a defense system it believes is necessary to ensure its security. Washington has expressed its concern over Ankara obtaining the Russian missile system. Russian experts will train Turkish military personnel on how to operate the system, which is set to be delivered in 2019.