Russia and PRC held several joint military drills. In geographical terms, the closest to home for NATO was the participation of Chinese guided-missile destroyer Heifei in Russian naval exercises in the Baltic sea in July 2017, as a continuation of 2015 joint naval drills in the Mediterranean and South China Sea.
- The Baltic Sea is in many ways NATO’s internal sea, with member states plus tacitly associated (but formally non-aligned) Sweden and Finland controlling almost all of its coast, and NATO’s Denmark and Norway locking the only passage into the ocean.
- The Baltic naval drills follow up the past Sino-Russian drills in the Mediterranian in 2015, which is also, for all practical purposes NATO’s internal sea.
- The Chinese are telling the US: “You mess up in the South China sea, be prepared for us to mess up in your neighborhood”. The Chinese won’t of course pick the fight so far from home, but they signal that they can strengthen the Russian hand.
- The Russians are telling the US: “We may not be able to deploy 200+ ocean-going naval ships like we did in the 1970s on our own, but together with the Chinese we can try to come close”.
- Supporting each other militarily, if the need arises, will require a totally different level of compatibility between the naval weapon, equipment and communication systems of China and Russia. Which language to use for what purpose? How to interpret intercepted commands from friendly forces? How to tell friend from foe from neutrals etc. That’s what naval exercises are for.