In pictures: The Ukraine-Russia crisis

After months of military buildup and brinkmanship on Ukraine’s border, Russia is ratcheting up pressure on its ex-Soviet neighbor, threatening to destabilize Europe and draw in the United States.

Russia has been tightening its military grip around Ukraine since last year, amassing tens of thousands of soldiers, as well as equipment and artillery, on the country’s doorstep. A whirlwind of diplomatic efforts in recent weeks has so far failed to defuse tensions in the region.

On Monday, Russian President Vladimir Putin ordered troops into separatist-held parts of eastern Ukraine in what the Kremlin called a “peacekeeping” mission, just hours after he signed decrees recognizing the independence of the Moscow-backed regions.

European countries and the United States have begun rolling out sanctions in response to Russia’s actions. US President Joe Biden described events underway in Ukraine as “the beginning of a Russian invasion” on Tuesday.

The escalation in the years-long conflict between Russia and Ukraine has triggered the greatest security crisis on the European continent since the Cold War, raising the specter of a dangerous showdown between Western powers and Moscow.