Russia wants a navy base. Period. It’s not a mystery. If you understand that Putin is supporting Assad for the purpose of having a navy base with a harbor that doesn’t freeze in the winter, and that is not cut off from the rest of the world by straights guarded by NATO, then Russia’s behavior becomes totally predictable and understandable.
How do I know this? Easy. Putin said as much. In 2008 if my memory does not fail me, he announced plans for a new oceanic fleet by 2020, with navy bases in Libya, Syria, Yemen, and Venezuela. Then came the Arab Spring and wiped away Kadaffi in Libya, and created civil wars in Syria and Yemen.
Russia already had a small base in Syria that seemed about to be lost, just like Sevastopol in Crimea would be lost when the treaty with Ukraine expired. Which is why Putin installed his man as president, but he was ousted in an uprising in 2014. So Putin invaded Crimea in order to hold on to Sevastopol. After that victory he turned to Syria and decided to hold on to that base as well, which is why he has backed Assad for a year now. Another stop gap measure has been a cooperation with Iran, using one of their bases in the Indian Ocean.
Libya and Yemen are out of reach now, but Venezuela is un unknown case. The area where the base presumably would be built has been closed off for civilians, and there are a lot of work going on under foreign direction. Not Russian though, but Asian. Tensions have gone high recently when foreign work leaders have pushed local crews beyond what they deem acceptable.
Russia is bombarding Aleppo because Putin wants a navy base in the Mediterranean, and his ticket to that is to keep Assad in power in Damascus no matter the cost. There are moderate rebels striving for a modern state, there are islamic extremist rebels, and there are some ethnic Turks and Kurds. This comes on top of the previous conflict in Iraq with Sunnis, Shias, and Kurds fighting each other, each with their links to kinfolks in other countries in the region.
The most problematic of these circumstances is the Kurdish case. It is the largest ethnic group in the world that does not have a country, a nation state. Their land is split between four countries, Turkey, Iran, Iraq, and Syria. Turkey is helping the moderate rebels in Syria against Assad but their main foe is the Kurds. Apparently the situation is as follows:
Russia's enemies: 1) moderate rebels, Kurds; 2) ISIS. Friends: Assad.
Turkey's enemies: 1) Kurds; 2) Assad; 3) ISIS. Friends: Moderate rebels.
USA's enemies: 1) ISIS; 2) Assad. Friends: Moderate rebels, Kurds.
There is one factor and one factor only that prevents the West from showing a united front, and it is the Kurdish problem. The fact that Turkey is insisting on subjugating a large tract of Kurdish land.
Turkey would have a lot to win on reconsidering its stance on Kurdistan. They would get more stability, and stability leads to economical development. It could also open the doors for EU membership. Furthermore, it would give them a friendly eastern neighbor that can act as a buffer to Iran, a very useful buffer since there are Kurds on the other side of the border as well, inside Iran. A Kurdistan created with pieces from present Iraq and Turkey would put Teheran on the defensive. By removing this problem from the table, all efforts could be focused on defeating the bad guys in the Levant (a people wanting sovereignty is not a bad guy!). It seems that it’s in Ankara’s interest to reconsider the Kurdish question.