Russian President Vladimir Putin has sparked one of the biggest security crises in Europe since World War II by invading Ukraine, with barrages of missiles and artillery accompanying troops as they entered the country from multiple directions.
Putin said he acted to protect civilians in separatist regions from Ukraine's military, though there was no evidence they were under any threat. The U.S. and European allies had warned for weeks that their intelligence showed Moscow planned to create a false justification for war.
Ukraine's government called Russia's actions a "full-scale invasion" and imposed martial law across the country. Ukraine's Interior Ministry urged citizens to go to shelters, saying the capital, Kyiv, was being targeted.
U.S. President Joe Biden said the "world will hold Russia accountable" for an "unprovoked and unjustified attack."
What's going on in Ukraine?
Russia's recognition of Ukraine's separatist Donetsk and Luhansk People's Republics and the treaties he signed with them gave Putin a pretext for sending "peacekeeping" forces to an area riven by conflict since 2014. But he's already gone well beyond that by attacking areas outside eastern Ukraine.
The U.S., Europe and U.K. are readying further sanctions on Moscow and the North Atlantic Treaty Organization said it would move more military assets into eastern Europe.
Putin had been demanding NATO roll back its presence to before its 1997 eastward expansion and rule out any accession for Ukraine. The alliance rejected those demands. Now Putin says he's looking to replace President Volodymyr Zelenskiy's government in Kyiv.
What's in Putin's Announcement of the Invasion?
Ahead of the offensive, Putin declared in a nationally televised address that action was necessary after the U.S. and its allies crossed Russia's "red lines" by expanding NATO. He also claimed Russia doesn't plan to "occupy" Ukraine.
NATO describes itself as a defensive alliance that poses no threat to Russia.
The Russian leader made other unsupported claims in his speech, saying the goal of the operation was the "demilitarization" of Ukraine.
Why does Russia want Ukraine?
Putin, a former KGB agent who was stationed in East Germany, has said he regrets the Soviet Union's demise and made clear that he does not accept Europe's post-Cold War security architecture.
He has offered a litany of complaints about the security risks to Russia of further NATO expansion and made the case that Ukraine was "completely created" out of land from the former Russian empire during the Soviet Union's formation. The implication was that he sees himself as on a historical mission to undo wrongs inflicted by Lenin's Bolsheviks.
Is Ukraine part of NATO?
Ukraine is not part of NATO, but some member nations have supplied weapons to help in its defense. The U.S. and NATO have said they would not send in troops in the event of an invasion.
NATO was founded in 1949 to protect Europe against Soviet attack during the Cold War and has come to symbolize the transatlantic alliance based on shared values. The pledge of collective defense, spelled out in Article 5 of the NATO treaty, established that an attack against one NATO member is considered an attack against all of them, increasing the risks for any potential aggressor. However, that does not apply to non-member Ukraine.
What sanctions are in place so far for Russia?
Biden's initial set of U.S. sanctions on Russia were criticized as underwhelming and limited in scope. But the penalties were added to within less than 24 hours with promises to ratchet sanctions still higher.
The European Union is banning the purchase of Russian government bonds and moved to sanction 23 high-ranking officials including banking executives, military chiefs, media chiefs and a top Kremlin official.
It remains unclear how much of an impact these measures will have on Russia, which is benefiting from high energy prices and high foreign reserves. Still, investors who shrugged off the initial measures took fright at the second wave, with markets sinking on Wednesday. And the West has made clear tougher penalties are now to come.