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 troops, equipment and artillery on the country’s doorstep. The aggression has sparked warnings from US intelligence officials that a Russian invasion could be imminent.In recent weeks, whirlwind diplomatic efforts to diffuse tensions failed to reach a conclusion.Moscow has repeatedly denied it is planning an assault, insisting instead that NATO support for Ukraine constitutes a growing threat on Russia’s western flank. An escalation in shelling in eastern Ukraine and a vehicle blast in separatist-held Donbas has heightened fears that Moscow could be stoking the violence to justify an invasion.The escalation in the years-long conflict between Russia and Ukraine has triggered the greatest security crisis on the continent since the Cold War, raising the specter of a dangerous showdown between Western powers and Moscow.So how did we get here? The picture on the ground is shifting rapidly, but here’s a breakdown of what we know.What has set the stage for the conflict?Ukraine was a cornerstone of the Soviet Union until it voted overwhelmingly for independence in 1991, a milestone that turned out to be a death knell for the failing superpower.After the collapse of the Soviet Union, NATO pushed eastward, bringing into the fold most of the Eastern European nations that had been in the Communist orbit. In 2004, NATO added the former Soviet Baltic republics Estonia, Latvia and Lithuania. Four years later, it declared its intention to offer membership to Ukraine some day in the distant future — crossing a red line for Russia.Russian President Vladimir Putin has indicated he sees NATO’s expansion as an existential threat, and the prospect of Ukraine joining the Western military alliance a “hostile act.” In interviews and speeches, he has emphasized his view that Ukraine is part of Russia, culturally, linguistically and politically. While some of the mostly Russian-speaking population in Ukraine’s east feel the same, a more nationalist, Ukrainian-speaking population in the west has historically supported greater integration with Europe. In an article penned in July 2021, Putin underlined their shared history, describing Russians and Ukrainians as “one people.”Ukrainians, who in the last three decades have sought to align more closely with Western institutions, like the European Union and NATO, have pushed back against that notion. In early 2014, mass protests in the capital Kyiv forced out a Russia-friendly president after he refused to sign an EU association agreement.Russia responded by annexing the Ukrainian peninsula of Crimea and fomenting a separatist rebellion in Ukraine’s east, which seized control of part of the Donbas region. Despite a ceasefire agreement in 2015, the two sides have not seen a stable peace, and the front line has barely moved since. Nearly 14,000 people have died in the conflict, and there are 1.5 million people internally displaced in Ukraine, according to the Ukrainian government.Read more here.