Good call!

https://en.wikipedia.org/wiki/Russia%E2%80%93Syria_relations

> an agreement was signed in February 1946 ensuring Soviet support for Syrian independence ahead of the evacuation of French troops in April 1946

> In 1971, under an agreement with President Hafez al-Assad, the Soviet Union opened its naval military base in Tartus

> On 8 October 1980, Syria and the Soviet Union signed a Treaty of Friendship and Cooperation

So, "how many years after it started" appears to be a negative number.

yes soviet union had diplomatic relations with Syria as well as other arab states, but Russia didn't involve in Syrian civil war instigated by the CIA (so called Arab Spring) and completely fumbled by Barry Soetoro

You're thinking about intervention as if it means direct military involvement. They were allied with Assad and supplying weapons the entire time.

Supplying weapons to whom? It was bona fide weapons purchases program from one state to another, like all other states procure their weapons.

Syrian war was civil war financed by the NED, USAID and other US entities to topple Assad, like they did in other arab spring states.

It took several years of civil war and unsuccessful bombing of civilians by Barry Soetoro, unsuccessful funding of various jihadi groups by the Pentagon and CIA (separately), the same groups that led to the rise of ISIS. Only then by the request from then president Assad, did Russia help with strikes against ISIS