One active U.S. intelligence official told The Daily Beast that while no one is “surprised to see reports of new Russian military equipment in the region—which would also suggest Russian forces training on that equipment—the line between training and taking part in combat is fuzzy. But the intelligence community also hasn’t seen anything to indicate that Russians are not taking part in the fight.”

Much discussed in U.S. defense circles is what the Israeli news portal YNet reported Monday, that a new “expeditionary force” of the Russian military has arrived in Damascus and converted a Syrian air force installation into its own forward-operating base. Russian pilots will also apparently start flying their own combat missions. “In the coming weeks,” YNet’s Alex Fishman wrote, citing Western diplomatic sources, “thousands of Russian military personal [sic] are set to touch down in Syria, including: Advisors, instructors, logistics personnel, technical personnel, members of the aerial protection division, and the pilots who will operate the aircraft.”

The goal is said to be purely counterterrorist in nature and conforms to a new period of bilateral cooperation between Moscow and Tehran in salvaging a common ally—Assad—while also amplifying the fight against ISIS. That war, as prosecuted by a U.S.-fronted coalition for a year now, has not been going so swimmingly.