President Biden took sharp aim at the Kremlin yesterday, saying Russia’s war in Ukraine amounted to “genocide” and accusing Vladimir Putin of trying to “wipe out the idea of even being a Ukrainian.” 

“Yes, I called it genocide,” the president said in comments made to reporters in Iowa on Tuesday shortly before boarding Air Force One to return to Washington. That drew praise from President Zelenskyy, who had encouraged Western leaders to use the term to describe Russia’s invasion of his country.

“True words of a true leader @POTUS,” Mr. Zelensky tweeted. “Calling things by their names is essential to stand up to evil. We are grateful for US assistance provided so far and we urgently need more heavy weapons to prevent further Russian atrocities.”

On Wednesday morning an advisor to the Ukrainian president, Mykhailo Podolyak, said via Twitter that “this is a step towards forcing the Russian Federation to sit on the dock. It is extremely important for our partners to give precise legal definitions of what is happening. To call genocide genocide is to bring an end to the massacres.”

Those words from Mr. Podolyak, who is seen as a key member of Ukraine’s team in the ongoing, if largely stalled, ceasefire negotiations with Moscow, underscore the delicate path carved out from Mr. Biden’s escalated rhetoric. While no new consequences for Russia were announced following his public assessment, the president has previously said: “More evidence is coming out literally of the horrible things that the Russians have done in Ukraine, and we’re only going to learn more and more about the devastation and let the lawyers decide internationally whether or not it qualifies.”

Past American leaders often have dodged formally declaring bloody campaigns like Russia’s as genocide, hesitating to trigger an obligation that under international convention requires signing countries to intervene once genocide is formally identified. That obligation was seen as blocking President Clinton from declaring Rwandan Hutus’ killing of 800,000 ethnic Tutsis in 1994 as genocide, for example.

Mr. Biden just last week said he did not believe Russia’s actions amounted to genocide, just that they constituted “war crimes,” making the White House’s ratcheting up of condemnation of Russia yesterday that much more telling. It comes on the heels of a steady trickle of just the kind of evidence that could in due course make it easier for lawyers to confirm that the tactics the Kremlin has been employing in Ukraine meet the international standard of genocide. 

Hundreds of innocent Ukrainian civilians were killed in small towns and suburbs outside the capital, Kyiv, in the run up to and during the retreat of Russian forces from these areas in late March and early April. The catalog of documented horrors includes deliberate shootings, mass graves, incinerated bodies on highways, and other atrocities that could eventually be prosecuted as war crimes.  

At least 410 civilians were killed in Bucha alone, including several who were found shot in the head with their hands tied behind their backs.

In eastern Ukraine, where the war is still raging, the staggering number of civilian deaths in Mariupol, a strategic port city pummeled by Russia for six weeks, also points to the sturdiness of Mr. Biden’s accusations of genocide. The city’s mayor, Vadym Boychenko said the death toll in Mariupol could surpass 20,000 and that bodies are “carpeting” the streets.

Mr. Boychenko also alleges that based on eyewitness accounts, Russian soldiers have been driving around Mariupol with mobile crematoriums and collecting bodies of civilians while simultaneously barring the International Committee of the Red Cross from entering the city with humanitarian aid. Such verbiage triggers connotations of the Holocaust, though it is unclear if it factored into the White House’s new evocation of genocide in Ukraine. 

In comments to ABC News last week, one U.S. lawmaker, Representative Seth Moulton, a Massachusetts Democrat who is a former Marine and a member of the House Armed Services Committee, lent credence to the Mariupol mayor’s charge. Mr. Moulton said that during a 2015 fact-finding mission in Ukraine, credible sources said that the Russian Army was using mobile crematoriums for its own soldiers in Russian-occupied Crimea to cover up the number killed there.

“None of that has changed. That is absolutely what was going on back then and I’m now hearing reports, unsurprisingly, that it’s happening again,” Mr. Moulton said. “The bottom line is this is nothing new for the Russian Army and Vladimir Putin.” 

Under international law, genocide can concern more than just race. A United Nations treaty, of which America is a signatory, defines genocide as actions taken with the “intent to destroy, in whole or in part, a national, ethnical, racial or religious group.”