Russian President Vladimir Putin's "special military operation” into Ukraine began on Feb. 24, with troops crossing the border from Belarus and Russia. Moscow's forces have since been met with “stiff resistance” from Ukrainians, according to U.S. officials.
Russian forces retreated last week from the Kyiv suburbs, leaving behind a trail of destruction. After graphic images emerged of civilians lying dead in the streets of Bucha, U.S. and European officials accused Russian troops of committing war crimes.
A look at the two leaders at the center of the war in Ukraine and how they both rose to power, the difference in their leadership and what led to this moment in history.
Here's how the news is developing. All times Eastern.
Mar 13, 2022, 5:52 PM EDT
Nearly 2.7 million people have left Ukraine
The United Nations High Commissioner for Refugees has calculated that 2,698,280 people have fled Ukraine since Feb. 24 as a result of the Russian invasion.
About 1.66 million people have entered Poland, 246,206 people have entered Hungary, and 195,980 people have entered Slovakia.
Nearly 200,000 people have entered Russia, Moldova, Romania and Belarus combined, while more than 304,000 people have entered other European countries.
-ABC News' Zoe Magee
Mar 13, 2022, 5:43 PM EDT
'Worst-case scenario' possible for thousands of civilians trapped in Mariupol: Red Cross
The International Committee of the Red Cross is calling for an urgent solution for the "life-and-death" situation facing the hundreds of thousands of civilians trapped in Mariupol without access to running water and electricity as the heavy airstrikes from Russian forces continue.
A "worst-case" scenario awaits those who remain in the city unless a humanitarian agreement among the fighting parties is reached immediately, the ICRC said in a press release on Sunday.
"We call on all parties involved in the fighting to place humanitarian imperatives first. People in Mariupol have endured a weekslong life-and-death nightmare. This needs to stop now," Peter Maurer, president of the ICRC, said in a statement. "Their safety and their access to food, water and shelter must be guaranteed."
People of all ages, including Red Cross staff, are sheltering in unheated basements and risking their lives to make short runs outside for food and water, according to the ICRC.
Anastasia Erashova cries as she hugs the one remaining living child of her three children in a corridor of a hospital in Mariupol, eastern Ukraine, March 11, 2022. Anastasia's other two children were killed during the shelling of Mariupol.
Evgeniy Maloletka/AP
Dead bodies, both of civilians and combatants, remain trapped under the rubble or lying in the open where they fell, and those suffering injuries or chronic, debilitating conditions are unable to seek treatment.
"The sound of warfare is constant. Buildings are struck, and shrapnel flies everywhere," said ICRC's operational leader in Mariupol, Sasha Volkov. "This is the situation every person in the city faces."
-ABC News' Zoe Magee
Mar 13, 2022, 5:29 PM EDT
American in western Ukraine describes 'bombs falling left and right'
An American who traveled to Ukraine to assist in the country's stand against the Russian invasion described the heavy bombardment parts of western Ukraine are now seeing.
Glock Dara, 29, was asleep at the military training ground in Yavoric, on the outskirts of Lviv, when he heard the first missiles begin to strike on Sunday morning.
"I didn’t have time to panic. I just focused on running as fast as I can," Dara told ABC News. "Hella chaos, bombs falling left and right -- you’re just praying to God it doesn’t happen to you."
The strikes left at least 35 dead and 134 wounded, according to Ukrainian officials. Russian officials claim 180 foreign mercenaries are dead.
Smoke rises amid damaged buildings following an attack on the Yavoriv military base, as Russia's invasion of Ukraine continues, in Yavoriv, Lviv Oblast, Ukraine, March 13, 2022 in this picture obtained from social media.
@BackAndAlive via Reuters
Dara is one of roughly two dozen soldiers evacuated from Yavoriv and brought to the Korczowa refugee center in Poland Sunday afternoon, about 15 miles away.
All of the men ABC News spoke with at the refugee center were volunteer foreign fighters from Ireland, France, Boston -- most dressed in uniforms bearing the Ukrainian flag. The base served as a launching pad for foreign fighters who were trained there and then deployed across the country, one medic from Ireland told ABC News.
"A lot" of Americans are at the American base as well, Dara said. He and some of the men he travelled with are now planning to re-group in Krakow, but Dara already intends to back to Lviv, he said.
"I came here as a volunteer counter-terrorist," he added.
The Korczowa refugee center has already seen a significant increase in the number of people coming in from western Ukraine in just the last couple days, volunteers at the shelter told ABC News.
-ABC News' Ines De La Cuerta
Mar 13, 2022, 4:52 PM EDT
Power lines repaired at Chernobyl nuclear plant
Ukraine Energy Minister Herman Galushchenko confirmed Sunday that power lines have been repaired to the Chernobyl Nuclear Power Plant in northern Ukraine, which was seized by Russian forces during a fierce battle last week.
"Our Ukrainian energy companies, risking their own health and lives, were able to avert the risk of a possible nuclear catastrophe that threatened the whole of Europe," Galushchenko said in a statement.
He said the restoration of electricity to the plant will enable its cooling systems of nuclear waste assemblies to work normally again, not from backup power.
In 1986, reactor No. 4 at the power plant, about 65 miles north of the capital Kyiv, exploded, spewing enormous amounts of radioactive material into the atmosphere and causing more than 100,000 people in a 1,000-square-mile radius to evacuate.
Nuclear experts and Ukrainian government officials had expressed concern about potential health hazards from radioactive material spreading from the defunct plant amid the fighting.