Russia is selling China its most advanced air defense system. Could this be a signal of growing military ties between the two economic partners?

Russia has confrimed that it has received advance payment from China for S-400 systems. As TASS reports:

The deliveries of S-400 air defense systems to China under this contract may begin in the first quarter of 2017, Chemezov said. Arguably the best air defense system on the market A source in the system of Russia’s military and technical cooperation earlier told TASS that Beijing would receive the first S-400 antiaircraft missile systems no sooner than in twelve or eighteen months. China’s deal to purchase S-400 Triumf systems was officially announced in the spring of 2015. Russia’s state arms seller Rosoboronexport Head Anatoly Isaikin didn’t disclose at the time the details of the contract, the number of S-400 systems that would be purchased by China or the timeframe of the deliveries. According to media reports, the deal involves no less than six S-400 battalions worth a total of $3 billion. The S-400 Triumf is the most advanced Russian medium- and long-range antiaircraft missile system that went into service in 2007. As many as 16 regiments of the Russian Army are expected to be armed with S-400 systems by the end of 2016. China has become the first foreign customer of S-400 antiaircraft missile systems.

The fact that China is the first nation to purchase the S-400 (remember, Iran purchased the S-300, and the systems haven't even been delivered yet) indicates that Moscow sees Beijing as a long-term political and military partner. Indeed, while the extent of Russia's "alliance" with China has been somewhat overstated, it seems that the growing economic ties between the two nations have facilitated closer military cooperation as well.

And we're already seeing how China and Russia are working together to protect their mutual security interests:

The foreign ministers of China and Russia are opposing the possible deployment of an advanced American missile-defense system in South Korea. Amid escalating tensions over North Korea's nuclear arsenal, Washington and Seoul last week began formal talks on deploying the sophisticated THAAD system. Chinese Foreign Minister Wang Yi told a news conference Friday after meeting with Russian counterpart Sergey Lavrov that putting the system in South Korea would "inflict direct harm to the strategic security interests of China and Russia."

And as the US continues to provoke China in the South China Sea, we expect further cooperation between Russia and China on political and military matters. Common economic and security interests have driven China and Russia together -- and Beijing's purchase of the S-400 is a perfect example.

How's that US "pivot to Asia" working out?