The distance between Caucasus........Armenia and Syria is about 400 km. Chechnya Dagestan etc are to the immediate North.
5,000--7000 Russian Muslims are fighting for ISIS.....Funneled, armed, trained, financed by NATO Turkey....puffed up like a croaking frog by their Western masters....Who used them before, against Russia.
Syria is Russia's only Arab ally, and a friend for 57 years since 1958.
Russia has military bases in Syria since before many years.
The Jewish lobby in Moscow lobbied to prevent Russian support for Syria....and this led to a period of bizarre, obtuse semantics from Lavrov...and even Putin.(Proposing a Russian initiative where Assad would step down, and al-Qaeda would take over in Damascus 2012)
But four years of fighting has made things much more clear for Russia.......ISIS can march against Damascus and Baghdad......ISIS can also march against Moscow.
Events in Ukraine from 2014 also helped Russia think more LOGICALLY and strategically.....to the point now, Russian military personnel are fighting in Syria, BUT not Ukraine.
Russia will destroy ISIS.
Though never made any sense how an irregular volunteer force, very lightly armed, trained of 10,000? could pin down two militaries of two sovereign countries, equipped with air-forces.......AND heavy equipment. This is not 500 BC. Heavy modern military equipment matter in flat desert like terrain.
Syria--350,000 armed forces not including the state militia....and Hezbollah, Pasdaran and Russian experts.
Iraq--200,000 including Pasdaran, and Shia militia's.
There's no point talking about the Western elements due to their dubious shady backgrounds.
US Condemns Move, Syria Confirms They Asked Russia for Help
by Jason Ditz, antiwar.com
A statement from the Syrian state media says President Bashar al-Assad formally requested help from Russia in the ongoing civil war, and that the airstrikes began in response to that. US officials slammed the move, saying Assad has to be removed from power.
The first Russian strikes targeted western Homs Province, with the Russian Defense Ministry saying they believe the positions hit belong to ISIS. Another rebel faction, however, claimed they were the ones that were hit, and also claimed Russia deliberately targeted civilians in the area.
According to US officials, Russia gave them an hour’s notice on the airstrikes, and advised them to remove US and coalition warplanes from Syrian airspace during the bombing run. There was no confirmation, however, if the US actually did this.