Six years ago, Russia entered the Syria war to bolster the Assad regime and helped push rebel forces back to the northwest fringes of the country. As the second international power to provide substantial support to the Syrian regime, Moscow has been critical to Assad’s military successes since 2015, with Russian airstrikes decimating rebel logistics chains, as well as civilian infrastructure. Directing a war between two ideologically divergent powers was no easy task but tolerable so long as both sides stuck to the simple equation – Iran took care of the manpower, while Russia provided air sup…