What are we doing in Syria?

It's not too hard to see what Russia is doing:

Russia joins war in Syria: Five key points

[...] The Russian president is one of Mr Assad's most important international backers.

Ties between their countries go back four decades and the Syrian port of Tartous is the location of the last Russian naval base in the Middle East. Russia has blocked several resolutions critical of Mr Assad at the UN Security Council and supplied weapons to the Syrian military, saying it is violating no international laws.

With Syrian government forces suffering a string of defeats to both rebel forces and IS over the past year, Mr Putin decided to intervene. In early September, Russian warplanes, attack helicopters, tanks, anti-aircraft systems and hundreds of marines arrived at a base in Latakia province.

Russian officials have reportedly said they are not intent on keeping Mr Assad in power, but they see his government as a bulwark against IS, which controls large parts of northern and eastern Syria.

Asked in an interview with CBS if his goal was "trying to save the Assad administration", Mr Putin replied: "You're right."

Russia's military build-up hints at wider involvement

Russia's deployment of air-to-air fighter aircraft and air-defence systems in Latakia suggests it may be preparing to do more than just carry out air strikes on IS and protect its base at Tartous.

Nato's Supreme Allied Commander Europe, Gen Philip Breedlove, warned on 28 September that Russia was developing an anti-aircraft "bubble" in the eastern Mediterranean. "These very sophisticated air-defence capabilities are not about [IS]," he said.

"High on Mr Putin's list in Syria is preserving the regime against those that are putting pressure on the regime, and against those that they see who might be supporting those putting pressure on the regime," the general added. [...]

There is a long history of support for Syria, it isn't something new. The Russian Navy base there, etc. So why the heavy military involvement NOW? By backing Assad and bombing all the rebels, Russia is insuring that the flow of refugees into Europe will continue. I think it may at least partly be payback for the sanctions Europe and the US have put against Russia for it's invasion of the Ukraine. Tit for tat.

The US state department is going on about supporting the Sunni rebels, replacing Assad, blah blah blah. They have nothing to back it up with, so what's the point of continuing with that? What are we doing in Syria anyway? Haven't we had enough of "Nation Building" in the Middle East?

If Europe and the US want Putin to cooperate, they will have to offer him something he wants. I would guess that would be the lifting of sanctions against Russia. Otherwise, Russia will stay on it's current course, and the refugees will just keep on coming. Duh. Am I wrong? Does it not make sense as a strategy?

Putin's playbook in Syria draws on Ukraine and loathing for revolution

[...] Some analysts see Putin as an opportunist, aware of Russian military and economic shortcomings but willing to take advantage of a vacuum or others' hesitation. Before moving to take Crimea, he knew the Ukrainian military was in a dire state and Kiev almost bankrupt. He was confident the United States and NATO would huff and puff but not dare to challenge him. The stakes were not high enough.

The same calculation applied to the rebellion in eastern Ukraine. Talk in Western capitals of arming the Ukrainians with offensive weapons such as missiles capable of taking out separatists' Russian tanks came to nothing. Sanctions were the preferred option -- cautious but eventually damaging.

Similarly, the failure of the West to stand up moderate opposition to al-Assad, its reluctance to engage capable Islamist groups such as Ahrar al Sham and help them take the battle to the regime, provided Russia with an opportunity to reshape the battlefield. Again, Putin calculated the West would and could not resist Russia's intervention. Was the U.S. likely to bomb the runway at Latakia? [...]

Read the whole thing for relevant history (which actually explains quite a lot), and a look the larger picture from several angles. Probable outcomes?