As if to prove his greatest adversaries on the international stage correct, Russian President Vladimir Putin launched a wide-ranging invasion of Ukraine on Thursday, hitting cities and bases with airstrikes or shelling, as civilians piled into trains and cars to flee. Ukraine's government said Russian tanks and troops rolled across the border in a "full-scale war" that could rewrite the geopolitical order and whose fallout already reverberated around the world.

In unleashing Moscow's most aggressive action since the Soviet invasion of Afghanistan in 1979, President Vladimir Putin deflected global condemnation and cascading new sanctions - and chillingly referred to his country's nuclear arsenal. He threatened any foreign country attempting to interfere with "consequences you have never seen."

Ukraine's president said Russian forces were trying to seize the Chernobyl nuclear plant, site of the world's worst nuclear disaster, and Ukrainian forces were battling other troops just miles from Kyiv for control of a strategic airport. Large explosions were heard in the capital there and in other cities, and people massed in train stations and took to roads, as the government said the former Soviet republic was seeing a long-anticipated invasion from the east, north and south.

The chief of the NATO alliance said the "brutal act of war" shattered peace in Europe, joining a chorus of world leaders who decried the attack, which could cause massive casualties, topple Ukraine's democratically elected government and upend the post-Cold War security order. The conflict was already shaking global financial markets: Stocks plunged and oil prices soared amid concerns that heating bills and food prices would skyrocket.

Condemnation rained down not only from the U.S. and Europe, but from South Korea, Australia and beyond - and many governments readied new sanctions. Even friendly leaders like Hungary's Viktor Orban sought to distance themselves from Putin.

Ukrainian President Volodymyr Zelenskyy cut diplomatic ties with Moscow and declared martial law.

"As of today, our countries are on different sides of world history," Zelenskyy tweeted. "Russia has embarked on a path of evil, but Ukraine is defending itself and won't give up its freedom."

After weeks of denying plans to invade, Putin launched the operation on a country the size of Texas that has increasingly tilted toward the democratic West and away from Moscow's sway. He made clear earlier in the week that he sees no reason for Ukraine to exist, raising fears of possible broader conflict in the vast space that the Soviet Union once ruled. Putin denied plans to occupy Ukraine, but his ultimate goals remain hazy.

In Washington, President Joe Biden convened a meeting of the National Security Council to discuss Ukraine as the U.S. prepares new sanctions. Biden administration officials have signaled that two of the measures they were considering most strongly include hitting Russia's biggest banks and slapping on new export controls meant to starve Russia's industries and military of U.S. semiconductors and other high-tech components.

Putin justified his actions in an overnight televised address, asserting that the attack was needed to protect civilians in eastern Ukraine - a false claim the U.S. had predicted he would make as a pretext for an invasion. He accused the U.S. and its allies of ignoring Russia's demands to prevent Ukraine from joining NATO and for security guarantees.

Among Putin's pledges was to "denazify" Ukraine. World War II looms large in Russia, after the Soviet Union suffered more deaths than any country while fighting Adolf Hitler's forces.

The Kremlin paints members of Ukrainian right-wing groups as neo-Nazis, exploiting their admiration for WWII-era Ukrainian nationalist leaders who sided with the Nazis. Ukraine is now led by a Jewish president who lost relatives in the Holocaust and angrily dismissed the Russian claims.

Putin's announcement came just hours after the Ukrainian president rejected Moscow's claims that his country poses a threat to Russia and made a passionate, last-minute plea for peace. The attack began at 5AM local time in Ukraine, on Thursday (Feb. 24), even as the UN Security Council was meeting to hold off an invasion. Members still unaware of Putin's announcement of the operation appealed to him to stand down.

UN Secretary-General Antonio Guterres opened the emergency meeting, telling Putin: "Give peace a chance." But hours later, NATO's Jens Stoltenberg indicated it was too late: "Peace on our continent has been shattered."

Mood for War

In the lead up to war, Putin laid out his version of Ukraine's history, saying essentially that Ukraine was always part of Russia. But Ukraine has its own thousand-year history.

What is now Ukraine was a contested region of shifting borders for centuries that did not come completely under Moscow's rule until late in the 18th century, during the reign of Catherine the Great, and even then the Russian Empire was never able to swallow it easily or completely, according to John Daniszewski, an AP vice president and former correspondent in Eastern Europe, who has written about European affairs since the 1980s.

In his present-day effort to bring an independent, Western-looking Ukraine back into Russia's orbit, Putin is following a well-trod path of many of Russia's rulers before him - from Peter the Great to Josef Stalin.

In a speech to the Russian public on February 21, a sometimes sullen, sometimes angry-sounding Putin was dismissive of modern-day Ukraine, arguing that its creation as a sovereign state was a tragedy and an accident of communist leaders in the 20th century.

Acting as though there had never been a historical Ukraine until Soviet times, Putin blamed at times Vladimir Lenin, at times Stalin and at one point he saved scorn for the decision of Nikita Khrushchev to take Crimea from Russia in 1954 and award it to Ukraine.

There were elements of truth in what Putin was saying. Ukrainians and Russians are related eastern Slavic peoples whose destinies have been both intertwined and separated throughout history. But he preferred to focus on the time of Russia's maximum dominance over Ukraine - neatly forgetting that it has been a separate state recognized by international treaties and explicitly by Russia over the last 30 years. Instead, he painted today's Ukraine as a corrupt, barely functioning puppet of the United States that threatens Russia's security and, in his view, has no real reason to exist except in union with Russia.

Both Ukraine and Russia trace themselves to Kievan Rus, a trading centre set up by Vikings along the Dnieper River more than 1,000 years ago, before Moscow even existed, that was originally pagan and later embraced Orthodox Christianity. Kievan Rus fell afterward to the early 13th century Mongol invasions of Europe. Muscovy did not emerge from being a vassal state until the late 15th century.

Instead of being connected to Russian Moscow, all of what is now Ukraine instead for centuries was part of the Grand Duchy of Lithuania from the 1300s, and later of the Union of Poland and Lithuania, a vast multilingual, multiethnic state whose territory encompassed almost all of what is now Poland, Lithuania, Belarus and Ukraine (and parts of what is now Russia.)

In its eastern and southeastern regions, the union's dominant languages were Polish and Ruthenian, the predecessor to modern-day Ukrainian and Belarusian. The population included Ukrainians, Poles, Belarusians, Lithuanians, Jews and Tartars.

Uprisings by an army of Ukrainian Cossacks against Polish lords and landowners in the middle 1600s led to a Cossack alliance with Moscow and eastern Ukraine breaking off from the Polish-Lithuanian Union and pledging loyalty to the czar in 1654. Western Ukraine remained part of the Polish-Lithuanian Union for another 150 years, until Poland was partitioned for the final time in 1795 and erased from the map of Europe.

Poland rose again after World War I and fought a territorial war with Soviet Russia between 1919 and 1922, winning back much of Ukraine. Those lands returned to Soviet control a generation later during and after World War II, but after the war Ukrainian nationalist partisans fought on against the Soviets in a guerrilla resistance for several years.

That the Bolsheviks recognised Ukraine as a separate socialist republic when the Soviet Union was created was no accident. It addressed the reality of Ukraine's separate history and identity, poised somewhere between Moscow and the West for most of its existence, but never given the chance to rule itself until the collapse of the Soviet Union in 1991.

Most Ukrainians do not clamour to be part of Russia today, and anti-Russian sentiment in most of the country has only increased since Russia's 2014 seizure of Crimea and the taking of the Donbas region by pro-Moscow separatists. Whatever support there is for Putin's actions is probably limited to this region in the east of the country, home to the two breakaway republics that Putin recognised as independent during his February 21 speech- Donetsk and Luhansk.

Laying the groundwork

According to a survey reported by German outlet DW, some 20% of the inhabitants of Donetsk said they were prepared to welcome Russian troops as their liberators. Around the same number wanted to fight for Kyiv.

In spring 2014, the administrations of several urban centres were occupied and police stations were stormed to seize weapons. Russian citizens with apparent links to the Russian secret services were the driving force. Subsequently, Moscow-backed separatists organized disputed referendums that sought to legitimize "self-rule."

Kyiv attempted to contain the insurgency. The Ukrainian army managed to regain control over most areas by summer 2014. But in August, the Ukrainian army suffered a defeat after being encircled in the battle of Ilovaisk, southeast of the city of Donetsk. Moscow still denies that regular Russian forces were involved. This put an end to major combat. The Minsk agreements of February 2015 laid down the front line. Since then, there has been a shaky ceasefire between the Ukrainian army and the Russian separatists.

In 2019, Russia began to distribute Russian passports to the area's inhabitants. According to the latest reports, some 800,000 eastern Ukrainians are said to have Russian citizenship - an estimated 15 to 25% of the population, although exact figures are hard to obtain. This is the central argument behind the Kremlin's recognition of the independence of the separatist regions.

Ukraine struggled to define the legal status of these regions. Initially, Kyiv described them as "terror organizations." Later, the Ukrainian parliament declared that Donetsk and Luhansk were occupied regions. However, Russia was not named as the occupying power until 2018. Under international law, they both remain part of Ukraine.

For decades now Moscow and Kyiv have been engaged in a dispute about language. Russia has long criticized the Ukrainian government, saying it discriminated against Russian speakers. Kyiv denies that. The fact is: The use of Ukrainian, as the country's only official language, has increased in the media and in written communication. However, Russian is spoken primarily in the cities of eastern and southern Ukraine while Ukrainian or a mixture of the two languages is spoken outside those urban centres. Two thirds of the inhabitants of the separatist regions say Russian is their mother tongue, according to a survey conducted by Berlin's Center for East European and International Studies (ZOiS) in 2019. About one in three people said they spoke both languages; only 3.5% said Ukrainian was their mother tongue.

The current mood among the population of the two regions can only be approximately gauged. According to the ZOiS study, which is three years old, about a third of the inhabitants of Luhansk and Donetsk were keen to gain autonomy within Ukraine or Russia. Almost 20% wanted to return to how things were before the split and just as many were in favour of becoming part of Russia without autonomous status. However, it is impossible to check the accuracy of these figures.

Additional reporting by agencies