Originally when Putin intervened in the Midde East War he said it was not to help Bachar al Assad : that was in 2014 and at the time Bachar was not very popular in Western eyes.
Now Putin asserts that he is only helping Bachar against the Islamic State and with weapon supplies. The military help is typical Russian Style help : towns are flattened and civilians are not spared !
What are Putin's aims ? To demonstrate that Russia leads the way and to encourage the West to join the fight on the Ground ? But, Putin must improve the Harbour Rights, which Russia has enjoyed in the port of Tartus on the Syrian coast since 1971 !
These facilities must be upgraded and modernised so that Modern Russian Warships can berth there. Then Russia would have a key presense in the Mediterranean basin. This would also enable it to send back-up supplies to Russian personnel, who are helping the Syrian Army to use Russian weapons.
However, at home Putin has problems ! To say the very least, the Rouble is weak, foreign currency reserves are low and there is mounting inflation. The Sanctions the West have imposed, because of his activies in Ukraine, are biting !
Something must happen soon !