NATO now estimates Russia has lost 40,000 of the troops it sent into Ukraine – killed, wounded, captured or missing. That means up to one-fifth of Russian forces have been neutralized. As a result, there's grave concern that a frustrated President Vladimir Putin will turn to what was once unthinkable: chemical or biological warfare.
It's why U.S. national security officials are preparing for a variety of scenarios in Europe.
It's also one of the issues prompting President Biden to meet with NATO and European leaders in Brussels on Thursday, calling on them to increase economic pressure on Russia. So far, Europe has balked at an embargo on Russian oil and gas. Biden is hoping to change that and continue the united front as a counter to Russian aggression.
"For the past few months, the West has been united," said National Security Advisor Jake Sullivan. "The president is traveling to Europe to ensure we stay united."
On Wednesday, the U.S. State Department formally accused Russia of war crimes in Ukraine.
Beth Van Schaack, the Ambassador-at-large for Global Criminal Justice, said carefully documented evidence shows Russian forces have targeted civilians. "Russia's forces have destroyed apartment buildings, schools, hospitals and other elements of the critical civilian infrastructure," she said.
In Mariupol, 100,000 people remain trapped as the Russians bombard their strategic port city and cut off necessities like water and electricity.
Thursday marks one month since Russia unleashed its invasion of Ukraine. The mayor of Kyiv says more than 260 have died.
Still, Ukrainian fighters have prevented the Russians from overtaking the capital and have even pushed the invading troops back to more than 30 miles outside of Kyiv.
A U.S. defense official says it appears Putin is now prioritizing Luhansk and Donetsk in the eastern Donbas region, hoping to cut off Ukrainian troops and prevent them from moving west.
Ukrainian President Volodymyr Zelenskyy is meeting with NATO leaders in a closed-door session Thursday, while he calls on the world to show solidarity by rallying in public squares to demonstrate support for Ukraine.
On Friday, President Biden travels to Poland which has opened its arms to more than 2 million of the 3.5 million Ukrainian refugees who have fled the country due to Russia's invasion. A U.S. official says the United States will welcome up to 100,000 refugees from Ukraine.