At least 8 Ukrainians reported dead hours after Russia launches invasion, with explosions heard across the country

• Russia attacked Ukraine early Thursday in what Ukraine called a "full-scale invasion."
• Missile strikes and explosions were heard across the country.
• Ukraine cut diplomatic ties with Russia and Western countries promised harsher sanctions.

Russian forces attacked Ukraine early Thursday morning in what Ukraine described as a "full-scale invasion" coming from multiple directions — a significant worsening of a yearslong conflict between the two countries.

At least eight Ukrainian civilians were killed and nine were wounded by Russian shelling, a Ukrainian internal affairs ministry advisor said, according to Reuters.

Forty Ukrainian soldiers and 50 Russian soldiers were aso killed in the fighting, Ukraine said, according to the Associated Press and Reuters.

Russia's offensive threatens to kill thousands of people, force millions more to flee, and destabilize much of Europe, with the consequences certain to reverberate across the world. 

'Full-scale invasion of Ukraine'

Blasts were heard from Kyiv, the capital, to the eastern city of Kharkiv, with reports of outgoing artillery fire from Russian forces across the border.

Russian tanks began pouring over the border from Belarus as well as occupied Crimea early Thursday, according to Ukraine's Interior Ministry, with Russian troops attacking Ukrainian security forces with artillery and small arms.

Ukraine's president declared martial law and said he would provide weapons to any citizen who wanted them to defend the country: "We will give weapons to anyone who wants to defend the country. Be ready to support Ukraine in the squares of our cities," he said.

Ukraine's foreign minister called Russia's actions "a full-scale invasion of Ukraine," with his ministry saying that Russian forces were "launching attacks on peaceful Ukrainian cities from different directions."

Missile strikes and explosions were heard in multiple places across Ukraine on Thursday, the BBC reported. 

Ukraine's border guard said early Thursday that Russian military columns had crossed into Ukraine and into three regions on Thursday: Chernihiv, Kharkiv and Luhansk, according to Reuters.

People have been fleeing Kyiv and using the city's subway stations as bunkers. 

Ukraine announced on Thursday that it was cutting diplomatic ties with Russia, and called on allies to do the same. It also said it was evacuating its embassy staff from Moscow.

NATO is due to hold an emergency session on Thursday, and the UK and EU promised to impose more sanctions against Russia.

Thursday's invasion was preceded by a formal request for military intervention from Russian-backed separatists in eastern Ukraine, where rebels and Russian forces have been fighting Ukrainian troops for eight years.

On Wednesday evening, Zelensky took to the airwaves in a last-ditch appeal for peace — while pledging that Ukrainians would "fight back" against any futher Russian incursion.

Hours later, in an early morning address that coincided with an emergency meeting of the United Nations Security Council, Russian President Vladimir Putin effectively declared war, insisting that Russian forces would strive for the "demilitarization" and "de-Nazification" of Ukraine, whose president is Jewish.

The road to war

Tensions had been mounting for months as Russia amassed troops, tanks, and amphibious ships near Ukraine's borders.

Beginning in late 2021, Russia began amassing tens of thousands of troops on Ukraine's borders, with roughly 190,000 deployed by the time of the attack. This build-up prompted Biden to conclude that an invasion was a near-certainty. 

Russia in mid-February claimed to be withdrawing some of its troops from Ukraine's borders, but the US and NATO didn't buy it, citing intelligence that the Kremlin had actually deployed thousands more soldiers.

Biden warned last week that he believes Russian forces will ultimately besiege Ukraine's capital, which has a population of nearly 3 million people. Earlier this week, he unveiled a new round of sanctions against Russian officials in response to Moscow deploying troops to the eastern Donbas region, which he characterized "the beginning of a Russian invasion of Ukraine."

This is not the first time Russia has assaulted Ukraine. In 2014, Russian troops annexed Crimea from Ukraine after a popular uprising topped the country's pro-Russia president. Since then, the Kremlin has supported rebels in a war against Ukrainian forces in the Donbas region in fighting that's killed over 13,000 people.

The latest attack came after a series of claims from Russia and Russian-backed separatists in eastern Ukraine — rapidly spread on social media — that Kyiv was planning a military operation to take back territory it lost control of some eight years earlier. Russia has maintained it was merely concerned with protecting Russian speakers in the region, asserting that they were subject to "genocide."

Biden dismissed such accusations in a speech earlier this month, accusing Russian forces of having "engaged in a false flag operation to have an excuse to go in." Ukrainian intelligence likewise accused Russia of planting explosives in buildings across rebel-held Donetsk.

The Biden administration warned Russia it would face severe economic consequences for invading Ukraine. But the White House has also been clear that US troops will not be deployed to defend Ukraine.

Thousands of US troops have been deployed to nearby NATO member countries, however, as a deterrent against further Russian aggression in the region. 

Over the past few months, the US and its allies worked to find a diplomatic solution to prevent a broader confrontation, but Russia made demands for binding security guarantees to which they would never agree. This included permanently banning Ukraine and Georgia from NATO, which the alliance and Washington repeatedly made clear was a non-starter.

Ukraine has sought to join NATO for years, and maintains robust ties with the alliance. The US since 2014 has provided Ukraine with billions in military assistance, including lethal aid like Javelin anti-tank missiles.

Other NATO members have also provided Ukraine with weapons. That said, Ukraine is not on track to become a NATO member in the near future, despite suggestions from the Kremlin to the contrary. 

For years, Putin offered hints of his ambitions when it comes to Ukraine. In 2008, he told President George W. Bush that Ukraine is "not even a country," and he's referred to Ukrainians and Russians as "one people."

In short, Putin has been clear that he wants Ukraine under Russian sway, and the US out of the region he perceives as in Russia's sphere of influence.

Putin, a former KGB operative, during his 20 years in power has moved to reestablish Moscow's hegemony in countries once part of the Soviet Union. The military operation he just ordered in Ukraine shows he's committed to this course, despite the risks that it will damage his economy or provoke a more robust NATO presence.