Russia aims to repurchase S-400 systems from Turkey

Turkey's Circumstances and Existing Projects
Turkey is a NATO member and has been developing its Steel Dome air defence system to lessen its reliance on Russian technologies. Turkish President Recep Tayyip Erdoğan stated that the S-400 systems would be fully operational by April 2020; instead, they have been set aside, are not part of NATO defences, and their missiles are now halfway through their shelf life. Upkeep has also become expensive for Turkey, and getting rid of the S-400s will open Turkey's communication in talks with Washington about F-16 fighter jets, and maximise Turkey's chances of being reinstated into the F-35 programme.

Russia's Shortages and International Obligations
Given that Russia is also subject to shortages of its own manufactured indigenous S-400, the Kremlin's interest in potentially reacquiring the two systems, which were delivered to Turkey in 2019 as part of a $2.5 billion deal (2017). Moreover, Russia is under pressure to deliver systems to its other buyers (i.e., India, which will not receive delivery until 2026–2027). This interest in reacquiring the systems stems from operational battlefield losses, as well as increasing available opportunities for the technology worldwide.

Background on the S-400 Agreement
The deal made with Turkey over the S-400 created friction between Russia and the United States, which resulted in Ankara being removed from the F-35 fighter jet programme and being subjected to sanctions. This will not be the last time the fate of Turkey's S-400 systems was debated on the battlefield, as Ankara rejected an offer to transfer its S-400 systems to Ukraine in 2023.