Here are the latest developments.

President Biden, who is in Europe to shore up allies’ support for Ukraine, on Friday heads to Poland, a key NATO member that has taken in millions of refugees from the war.

His visit comes a day after NATO approved deploying 40,000 additional troops to Eastern Europe and activated a special military task force to respond should Russia use weapons of mass destruction. It also comes as Ukrainian forces have launched several counteroffensives that appear to have changed the dynamic of the war.

After a meeting in Brussels on Friday morning with the European Commission’s president, Ursula von der Leyen, Mr. Biden is scheduled to fly to Rzeszow, Poland, a city close to the Ukrainian border, where he will be briefed on the humanitarian crisis and then visit American soldiers with the 82d Airborne Division who are stationed there.

The American troops are in Poland as part of NATO’s military buildup in Eastern Europe in recent months. NATO said on Wednesday that it would increase to 40,000 the number of troops in the region under its direct command. About a quarter of those troops are in Poland, more than in any other country in Eastern Europe.

Mr. Biden is also expected to meet with refugees who have come into Poland over Ukraine’s western border. On Thursday, he announced that the United States would accept 100,000 Ukrainian refugees and donate $1 billion to help European countries deal with the refugee crisis, the biggest the continent has faced since the end of World War II.

On Saturday, Mr. Biden is scheduled to meet with the president of Poland, Andrzej Duda, in Warsaw. He will address the people of Poland from the Royal Castle before boarding a plane back to Washington.

In other major developments:

More than half of Ukraine’s children — about 4.3 million so far — have been displaced by the war, according to UNICEF.

Two Russian missiles struck a military base in Dnipro, a city in central Ukraine, late Thursday, a local rescue service said. No information about potential casualties was immediately available.

Russia and Ukraine carried out their first prisoner exchanges since the invasion began, Deputy Prime Minister Iryna Vereshchuk of Ukraine said.

For some older Ukrainians, Russia’s invasion has revived painful memories of World War II.

About 56 percent of Americans said Mr. Biden had not been “tough enough” in his response to Russia, according to a poll by The Associated Press and NORC. Read more

@nytimes