Russia stunned the U.S. on Wednesday by giving it just a one-hour heads-up that it was going to pummel ISIS targets. U.S. aircraft should stay out of the way, it said.
The problem, analysts say, is that Russia doesn't seem to be pounding ISIS targets. Instead, they say, Russia appears to be attacking rebels to help crush Syrian dissent and bolster Syrian President Bashar al-Assad.
Either way, Russia's new attacks can have big ramifications not just for the Syrian civil war, but for the U.S.-led coalition fighting ISIS.
Russia said its airstrikes in Syria came at the request of al-Assad. And the Kremlin said it's coordinating its targets with the Syrian regime.
The Russian Defense Ministry said warplanes targeted eight ISIS positions Wednesday, including arms, transportation, communications and control positions.
But the targets aren't limited to ISIS, Kremlin spokesman Dmitry Peskov told the state news agency Tass.
"This operation is aimed at supporting the Syrian armed forces in the fight against the Islamic State terrorist group (banned in Russia) and other extremist groups," Peskov said.
The phrase "other extremist groups" is critical. Since the beginning of Syria's four-year civil war, al-Assad has referred to his opponents as "terrorist groups" -- starting well before ISIS became a serious threat in Syria.
That raises the possibility that Russian airstrikes could land on Syrian rebels and civilian dissidents. And that could escalate the massive refugee crisis
that has sent millions of Syrians fleeing to other countries.
Why does the Pentagon doubt Russia's targeting ISIS?
The Russian attacks Wednesday didn't appear to hit targets under the control of ISIS, which operates in the north and east of the country, U.S. Defense Secretary Ash Carter said.
And a senior U.S. administration official said a Russian airstrike near the Syrian city of Homs "has no strategic purpose" in combating ISIS, which "shows they are not there to go after ISIL" -- another acronym for ISIS.
The Institute for the Study of War
said Russian airstrikes appeared to target Syrian rebels, not ISIS.
"Russian warplanes conducted 20 airstrikes on the rebel-held towns of Rastan and Talbisah north of Homs City, as well as on the towns of Al Latamneh and Kafr Zeita in Hama Province," the institute said.
It added that "local Syrian sources claim the airstrikes exclusively targeted rebel positions."
Who else is unconvinced?
France, part of the U.S.-led coalition striking ISIS targets in Syria, said it is also questioning Russia's true motives.
"We have to check that it really was Daesh and terrorist groups that really have been targeted and not opponents to the Syrian regime or the civilian population," French Foreign Minister Laurent Fabius told reporters Wednesday. Daesh is the Arabic acronym for ISIS.
"I'm not accusing anybody of anything, but we have to check the facts," he added.
But the Syrian National Coalition, a dissident group, reported 36 people were killed in the Russian airstrikes -- all civilians.
How dangerous can this get?
Lots of military jets from different countries flying in cramped airspace could be disastrous.
"This is going to get very dangerous," CNN military analyst and retired Lt. Col. Rick Francona said Thursday.
"Right now you've got the aircraft of the Syrian air force, the Russian air force, and the U.S.-led coalition operating in a very confined area. These are high-performance aircraft -- lots of weapons, lots of people on edge when they're flying these missions."
He said any mistake "could result in an incident with fatalities on somebody's side."
Has anyone besides Syria welcomed Russia's airstrikes?
Iraqi Prime Minister Haider al-Abadi said Russian airstrikes in Syria are "beneficial." He said he would welcome Russia's expansion to his ISIS-plagued country if Moscow joins the U.S.-led international coalition effort.
"Don't forget, Iraq was attacked from across the Syrian border into Iraq by Daesh, by ISIL," al-Abadi said in an interview with PBS.
"And that cost us a lot of human costs in terms of people killed, people being kidnapped, people being enslaved, women, children. So any joining of this fight against Daesh by anyone, we very much welcome."
So why does Russia support al-Assad?
Russia has long been a staunch ally of Syria -- even as other world leaders say al-Assad's regime has killed tens of thousands of civilians and must go.
Syrian dissidents have been demanding an end to over 40 years of al-Assad family rule. But what started as peaceful protests in 2011 led to a violent government crackdown and now a full-blown civil war, with more than 200,000 people killed -- mostly civilians.
Moscow has been allies with al-Assad's family since the Soviet days, when it was the main military supporter of al-Assad's father four decades ago.
It supplied hundreds of military advisers in the 1967 war against Israel and billions worth of sophisticated equipment since.
In return, it got a lease on a naval supply depot in the port of Tartus. That base is critical because Russia had no other reliable port facilities for its navy in the Mediterranean Sea.
On top of that, the Syrian regime has been a big customer for Russian weapons
, with billions of dollars in estimated spending.
What else does Russia stand to gain?
The U.S. intelligence community now suspects Russia beefed up its military strength in Syria because al-Assad may not be able to hang onto power -- and Moscow wants to position itself to back a proxy if the regime were to collapse.
The Pentagon has the same suspicion, Department of Defense officials told CNN.
Russia's bold move in Syria "will clearly signal to regional and international powers Russia's determination to prevent Assad's ouster," said Ayham Kamel of the Eurasia Group, a political risk consultancy.
Ultimately, Russia's intervention is a game-changer in Syria, the Institute for the Study of War says.
"It will alter the nature of international negotiations, compromise and weaken the cohesion and efforts of the U.S.-led anti-ISIS coalition (and) strengthen the Assad regime."