“We won’t give them any of the electronic codes or ‘internals.’ Under the agreement, technical servicing will only be done by Russia and they [the Turks] won’t gain entry to the systems,” a Russian military source told Gazeta.ru.

According to Gazeta.ru, this applies to one of the weapon’s key elements: The friend-or-foe identification system.

“We did not agree to their demand to allow access to the S-400’s internals, therefore the systems will have a friend-or-foe identification system made in Russia. Turkey insisted on us passing on the passwords and control to them but we refused to do so,” the source said.

At the end of September Turkey transferred the first payment for the S-400 system. According to Viktor Murakhovsky, editor-in-chief of the Arsenal Otechestva magazine, Ankara won’t receive the first systems until 2020.

“At present Russia is completing the rearmament of its own army with the S-400s and after that it will have to meet its obligations to China and India for these systems. Accordingly, only after that will Almaz-Antei start assembling S-400 systems for Turkey,” he told Russia Beyond.