Syrians are already all too familiar with the atrocities that Russia has been committing in Ukraine: the attacks on hospitals and schools, the use of banned munitions against civilians, the wielding of starvation as a weapon of war. Russian hasn’t yet used chemical weapons, but that could be just a matter of time. “I would not be surprised if we saw that happen soon in Ukraine,” McCaul said.

Rep. Brendan Boyle (D-Pa.) said Putin is using the “Aleppo playbook” in Ukraine, referring to the multiyear campaign of large-scale bombing and sieges that Assad, Russia and Iran used to subdue Syria’s second-largest city, which fell to the regime in 2016.

“I firmly believe that if the world had reacted to Syria as they are now, there never would have been a Ukrainian invasion to begin with,” Boyle said. “We should use this as an opportunity to recognize the reality that Putin will keep doing this in other places if he’s not stopped.”

Stephen Rapp, who served as the State Department’s ambassador-at-large for war crimes during the Obama administration, said that if the international norms against mass atrocities, war crimes and crimes against humanity are allowed to erode further, mass atrocities will continue to proliferate.