There’s no clear way the United States can defeat the Islamic State in Syria and remove President Bashar al-Assad from power without President Obama working together with President Vladimir Putin. Not only must the United States and the European allies coordinate with the Russian leader to carry out airstrikes against the Islamic State, we need his assistance to negotiate an inevitable exit for Assad in order to end to Syria’s civil war.

And while it’s understandable that some Russia watchers and members of Congress want the United States to have nothing to do with Putin, we’ve reached a point where countering the threat presented by the Islamic State overrides the risks.

It’s true that before last Friday’s attacks in Paris, for which the Islamic State claims responsibility, the idea of working closely with Putin seemed remote. During Obama’s second term, Putin is increasingly viewed by Americans as more foe than friend. It’s fair to say that Russia helped thwart Obama’s 2013 drive for military action in Syria and that recent actions in another theater, eastern Ukraine and Crimea, run counter to U.S. and European interests. Instead of allowing Ukrainians to navigate the travails of their 2014 political uprising, Putin provided safe haven for their deposed former president, backed anti-Kiev rebels that have been waging war in the country’s east for more than a year and a half, annexed Crimea by force and has been less than cooperative in honoring the Minsk peace accord designed to end the conflict.

“Mr. Obama,” writes the Russia Studies Center’s Andrew Foxall, “should not be fooled,” because trusting Putin to set terms for cooperation “risks repeating past mistakes.” And by blocking American efforts in the U.N. Security Council to counter Assad, argues Sen. Robert Menendez (D-NJ), Putin effectively “brought us to this point in the first place.”

As troubling as Putin’s behavior has been, however, the consequences of his actions in Europe pale in comparison to the stakes in Syria. If we ever hope to see Assad gone — a condition precedent to any meaningful cessation of Syria’s civil war — the Islamic State forced out and a stable transitional government that is willing to work with the West, we have to work with him. Obama seems to be coming around to this point of view, saying Wednesday, “If we get a better understanding with Russia about the process for bringing an end to the Syrian civil war, that obviously opens up more opportunities for coordination with respect to ISIL.”

During a 30-minute meeting between the two leaders on the sidelines of the Group of 20 summit in Antalya, Turkey, on Sunday, Putin expressed support for a Syrian-led transition away from the Assad regime. Monday, he announced he would back parts of the Syrian opposition with airstrikes against the Islamic State. If he follows through on his promises, it could be a game-changer.

We’re prompted to not trust his motives, but Putin has incentives to follow through: Russia confirmed Monday that Islamic State operatives detonated a bomb that downed a Russian passenger jet in Egypt, killing 224. Russia is already coordinating airstrikes with the French military in response to the Paris attacks.

Wariness understandably remains. Since September, when Russia first began flying sorties in Syria, most of their airstrikes reportedly targeted Syrian combatants who are anti-Assad, U.S.-backed and not Islamic State. But given where we now stand, Putin’s trustworthiness isn’t the only question to consider.

Western leaders should be asking what outcome we want in Syria and whether it can be achieved without Putin. The answer, very likely, is: no.

Who is best positioned to negotiate a transition plan for Assad to leave Damascus? Putin — as Assad’s patron, he has leverage. In the event Assad goes, with whom must we negotiate to ensure a peaceful transfer of power? Again, Putin. He wants to maintain Russia’s naval base in Tartus, Syria, and, more broadly, a stake in the Middle East. He won’t simply withdraw troops from Syria after brokering a deal for Assad’s departure if Assad’s successor isn’t seen as amenable to Russian interests — that would defeat Putin’s purpose for working with Western powers in the first place. Whose military is best positioned for an end-stage fight against the Islamic State? Putin. Russia is the only major power with a critical mass of boots on the ground. And Obama has shown little interest supplanting Russia’s position with U.S. troops.

In the current scenario, interests align. The Europeans, like the United States, also prefer to see Assad gone and a new government that’s at least warmer, if not actually warm, to the West. They also want to stem the wave of refugees entering the European continent to escape Syria’s civil war — which has forced 4.2 million people to claim refugee status, according to the United Nations. So far, 681, 713 of them have applied for asylum in Europe between 2011 and October of this year. Many countries, especially those in Eastern Europe, have been resistant to accepting them, but if working closely with Putin can reverse this, it’s reasonable to think Europeans will grit their teeth and partner with Russia to make that happen.

As for the candidates seeking to succeed Obama, many have echoed the sentiments of Sen. Marco Rubio (R-Fla.), who once referred to Putin as a “gangster” to press the point that in the past, Obama has allowed Russia’s president to take advantage. Putin may well be a gangster, but we don’t require heads of state to pass a morality test before we work with them — especially if the relationship can benefit our national interests.

Uzbekistan has one of the worst human rights records in the world, but that hasn’t stopped successive administrations from working with President Islam Karimov because Washington believes his help is crucial in fighting al-Qaeda in Afghanistan. In President Gurbanguly Berdymuhamedov’s Turkmenistan, basic rights are denied. But during the Afghanistan conflict, the American military has operated air bases in Turkmenistan and used their airspace for overflights.

You’d be hard pressed to call these leaders honorable, but engaging them has been viewed as crucial to U.S. foreign policy.

And that’s what it comes down to with Putin: We don’t have to like him — or another Russian leader — to work with them. If that were the case, Franklin D. Roosevelt wouldn’t have allied with the Soviet Union to fight Nazi Germany in World War II, despite Joseph Stalin’s history of abuses against his own people. History now views John F. Kennedy as wise for agreeing to withdraw U.S. missile installations from Turkey in order to resolve the Cuban missile crisis. Ronald Reagan built a political legacy highlighting the “weighty differences” between the United States and the Soviet Union, but worked with Mikhail Gorbachev to conclude a treaty reducing each nation’s nuclear arsenal.

Simply put: America can’t afford to balk at dealing with world leaders, even those we may consider adversaries. If we want Assad and the Islamic State out of Syria, Obama has to work with Putin, the same way his predecessors engaged their Russian counterparts.