Later this year, Serbia will take part in Collective Security Treaty Organization drills as a full-fledged member for the first time; the other six nations which comprise the regional military alliance are all close Russian allies and former Soviet republics.

September 2017 will see Serbia's full-blown participation in the war games of the Collective Security Treaty Organization (CSTO), according to media reports.
The CSTO, which includes Armenia, Belarus, Kazakhstan, Kyrgyzstan, Russia and Tajikistan, was set up by the former Soviet states in 1992 shortly after the collapse of the Soviet Union, in a bid to facilitate cooperation and strengthen security in the region.

Serbia and Afghanistan have observer status at the CSTO Parliamentary Assembly.

The upcoming CSTO drills, dubbed "Indestructible Brotherhood," will be held in Kazakhstan; Serbia's army and police units are due to take part.

"Given that the Serbian military already participated in similar previous exercises involving Russia and Belarus, Belgrade's cooperation with the CSTO in this sector looks logical," Serbian political scientist Dusan Prorokovic told Sputnik.

https://sputniknews.com/europe/201704101052476823-russia-serbia-military-exercises-cooperation/