It is also possible that bases in Iran would give them easy access to targets in northern Iraq. Of course, I am sure they would not pass up the opportunity to establish bases in Iraq.
The Russians have decided they have major economic and geopolitical goals to accomplish in the Middle East. The vacuum of power cause by US efforts to withdraw, ally with jihadists in Libya and Syria to make them hate us less and then trying to lead from behind has created conditions more favorable to the Russians than anything since the 1960s.
So the cost of this operation is well worth it to them. They are attempting to build an Iron Curtain across the Middle East, from Syria (and Lebanon under Hezbollah) across Iraq to Iran and probably further. As NATO retreats from Afghanistan, expect the non-Taliban factions to go to the Russians for support against Pakistan and their proxies. Followed by efforts to woo, India into their anti-Sunni extremist alliance.
Controlling that line gives Russia major control over the world economy. It prevents a proposed natural gas pipeline from the Middle East to Europe keeping Europe dependent upon Russian Gazprom to avoid freezing. So controlling Syria forces Europe to allow Russia to continue gobbling up neighboring regions in Ukraine and other places. The Russians are also hoping to force Poland and other states to leave NATO because they believe NATO would not defend them. Alliance with the Iranians also provide the Russians the ability to close the Persian Gulf oil flow disrupting the rest of the world oil supply.
All the while the Russians will be telling everyone that they have saved the West from ISIS, because the West was too weak to win the War on Terror. While it is true the West is not too weak to win that war, the West has shown 14 years of being unwilling to win the war. We will soon see if the War can be won using hard power, when the West was unwilling to do so.
I suspect the Russians may pull it off for several reasons.
1. The Russians will apply enough fire power to make a difference, unlike the West trying to use proportional force.
2. The Russians don't abandon their allies. The US problem in the Middle East is that so few powers will go in as our allies because they know by the next election cycle the US will throw them to the wolves.
3. Because of #2, the Russians have allies with sufficient ground power to complement their air power. And the arrival of competent allies at a critical time has convinced them they can win.
4. The Russians learned from Chechnya that they can crush a jihadist movement, as long as they are willing to do maximum damage and consider the collateral damage a benefit not a detriment.
5. With the break up of sanctions against Iran, Russia will arm them and the Russian presence will deter any attacks against Iran and Syria's nuclear program allowing both states to become nuclear powers. Pakistan has already sold nuclear missiles to Saudi Arabia with delivery guaranteed upon Iranian deployment of nukes. Unfortunately, I doubt a Middle Eastern nuclear armed Cold War will stay cold forever.
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