It took less than two weeks for one of the worst dictatorships in the world to fall. The end of the Assad dynasty in Syria signifies a clear win and major opportunity for the U.S. and its allies. That opportunity will evaporate quickly, however, if the U.S. fails to recognize the importance of what just happened.

Bashar al-Assad’s Syria was the crucible for regional conflict and instability that drew in great powers, along with a multitude of actors competing for influence. It was a hub of terrorism in the Middle East, giving strength to groups like ISIS, al-Qaeda and Hezbollah.

Assad’s chief backer, Russian President Vladimir Putin, saved Assad in 2015 and expanded Russia’s military presence in Syria to project power against NATO’s southern flank, southern Europe overall, the Middle East and Africa. Now Russia, bogged down in Ukraine, has shown that it was either unwilling or unable to save its client in Damascus.

The overthrow of Assad by rebels led by Hayat Tahrir al-Sham — a group that grew from an al-Qaeda affiliate but now promises to moderate Assad’s worst atrocities — may be a mere illusion of progress. Nonetheless, Assad’s fall represents a severe blow to Putin’s prestige, and a brief opportunity for the western coalition and the U.S.

The road to wider peace in the Mideast cuts through Syria, now thrust into yet another cycle of upheaval. Putin lost this round, but he has not been knocked out of Syria. The Kremlin is positioning itself with the new government to make it uphold its interests.

Russia’s official state media no longer refers to Assad’s opposition as “terrorists” as they have done consistently over the years, a clear signal to anti-Assad rebels who reportedly gave Russia security guarantees for its military bases and diplomatic institutions in the country.

Kremlin spokesperson Dmitry Peskov told journalists that Russia is taking all the “necessary steps to establish contact in Syria with those capable of ensuring the security of military bases.” Moreover, Russia is a co-signatory to the one document that outlines a process for Syria’s political transition, UN resolution 2254.

Russia has already granted Assad and his family asylum and called for a Security Council meeting on Syria in the hope of preserving its role in Syria’s future. For Russia, Syrian’s future will not be about securing genuine peace, but preserving Russia’s influence and power through continued instability in the Middle East and opposition to the United States.

Indeed, Russia’s role in Syria was never about securing the Assad regime, nor even about defending Syria itself, but about the power and influence Russia sustains through conflict. The question is whether the U.S. recognizes the historic opportunity presented by the overthrow of Assad to bring about a better vision for the country, or chooses to forgo it.

As is usually the case, what happens in Syria reverberates far beyond the country. At a time when President-elect Trump signaled the U.S. should not be involved in Syria and called for an immediate ceasefire on Ukraine, some Russian commentators have pointed out that Assad’s fall may actually harden Putin’s position on Ukraine, making him even less willing to compromise.

Putin also has a tendency to lash out when backed into a corner, and losing in Syria could cause him to escalate elsewhere to scare the West into concessions, as it did with the recent use of the experimental Oreshnik nuclear-capable missile against the Ukrainian city of Dnipro. In other words, today Putin’s Russia is overstretched and resource-constrained, but still has moves left. Russia is wounded in Syria, but will recover if left uncontested.

Washington should take the lead in the Syria diplomatic process and box out Moscow: If the U.S. is absent, Russia will cut a deal with any ruling authority. Now is the time to ensure Russia loses its military bases in Syria.

Putin is halfway out the door from Syria. The U.S. can secure our interests in the Eastern Mediterranean, the Middle East and beyond by pushing him the rest of the way.