The obvious problem with Putin's grand coalition argument at the UN
"The power vacuum [in the Middle East] … has started to be filled by militants and terrorists," the Russian president said. "... We think it is an enormous mistake to not cooperate with the Syrian government and its armed forces," the Russian president said.
"On the basis of international law, we must create a genuinely broad international coalition against terrorism."
But there's an obvious problem with his argument: By propping up the regime of Syrian President Bashar al-Assad, Moscow is actually facilitating the continued menace of ISIS.
"The [Syrian] regime is a terrorism generator of epic proportion, engaging in state terrorism against its own people and inciting terrorism from its opponents," the strategic security firm The Soufan Group noted last month.
"There is no justifying the actions of a group like the Islamic State or al-Nusra ... but the Assad regime's wholesale slaughter of civilians provides the groups with radicalized supporters far faster than Assad's military can then fight them."
Russia has been increasing its military presence in Syria since the end of August - under the guise of helping the embattled Syrian president fight ISIS and other extremists.
But many experts have noted that Putin's priority is not to get rid of ISIS, but to keep Assad in power against all rebels.
"The [Russian] deployment is clearly designed to shore up the regime's military capabilities, which have shown serious signs of weakness since March, when the rebels made a string of swift gains in different parts of the country," Middle East expert Hassan Hassan told The New York Times.
Assad is threatened by other rebels groups much more than ISIS. Therefore, as Russian strategic analyst Igor Sutyagin pointed out in a new report, Russia will be helping fight the rebels that are fighting both Assad and ISIS.
"In this way, Russian troops are backing Assad in the fight against groups such as Jabhat al-Nusra and Ahrar al-Sham, which are themselves opposed to ISIS," Sutyagin argued, as reported by The Guardian. "If Russian troops do eventually join combat, therefore, they would also - technically - be assisting ISIS."
"By releasing dozens of al-Qaida prisoners in mid-2011, Assad helped give birth to a thriving Islamist insurgency, including an al-Qaida affiliate," Charlies Lister of Brookings wrote in a piece Monday.
"By then adopting a deliberate policy of not targeting IS, Assad directly facilitated that group's recovery and explosion into the transnational 'caliphate' movement it claims to be today."
And many experts agree that giving into Assad's continued reign would only make the situation worse.
Nevertheless, it now seems as though Putin is getting his way, as more and more Western leaders - including British Prime Minister David Cameron and US Secretary of State John Kerry - are accepting the notion that Assad will stay in power as a transition is negotiated.
President Barack Obama, who is set to meet with Putin later in the day Monday, blasted Putin's Syria policy in his own address to the UN Monday. But he only called for a "managed transition" from Assad to another leader.
"I think today everyone has accepted that president Assad must remain so that we can combat the terrorists," Iranian President Hassan Rouhani, an ally of Assad's regime, told CNN in an interview.
"The West must not fall for Putin's trap," Kristina Kausch, head of the Middle East and North Africa Program at the Spanish think tank FRIDE, told the Carnegie Foundation last week.
"As long as Syria's choice is framed as ISIS vs. Assad, both will prevail."