On 24 February 2022, Russia invaded Ukraine, marking a steep escalation of the Russo-Ukrainian War, which had begun in 2014. The invasion has caused Europe's fastest-growing refugee crisis since World War II, with more than 6.8 million Ukrainians fleeing the country and a third of the population displaced.
At the start of the war in 2014, Russia invaded and annexed Crimea, and Russian-backed separatists seized part of the Donbas, the south-eastern region of Ukraine (consisting of Luhansk and Donetsk oblasts), sparking a regional war. In 2021, Russia began a large military build-up along its border with Ukraine, amassing up to 190,000 troops and their equipment. In a televised address shortly before the invasion, Russian president Vladimir Putin espoused irredentist views, challenged Ukraine's right to statehood, and falsely accused Ukraine of being governed by neo-Nazis who persecute the ethnic Russian minority. Putin also alleged that eastward expansion by the North Atlantic Treaty Organization (NATO) threatens Russia's national security, something NATO has disputed. Russia demanded NATO stop expanding and permanently bar Ukraine from ever joining the alliance. Multiple nations accused Russia of planning to attack or invade Ukraine, which Russian officials repeatedly denied as late as 23 February 2022.
On 21 February 2022, Russia recognised the Donetsk People's Republic and the Luhansk People's Republic, two self-proclaimed breakaway statelets in Donbas controlled by pro-Russian separatists. The following day, the Federation Council of Russia authorised the use of military force abroad, and Russian troops overtly entered both territories. The invasion began on the morning of 24 February, when Putin announced a "special military operation" to "demilitarise and denazify" Ukraine. Minutes later, missiles and airstrikes hit across Ukraine, including the capital Kyiv, shortly followed by a large ground invasion from multiple directions. Ukrainian president Volodymyr Zelenskyy enacted martial law and a general mobilisation of all male Ukrainian citizens between 18 and 60, who were banned from leaving the country.
At the start of the invasion, Russian attacks were launched on a northern front from Belarus towards Kyiv, a northeastern front towards Kharkiv, a southern front from Crimea, and a southeastern front from the cities of Luhansk and Donetsk. During March, the Russian advance towards Kyiv stalled. Amidst heavy losses and strong Ukrainian resistance, Russian troops retreated from Kyiv Oblast by 3 April. On 8 April, Russia announced that its forces in southern and eastern Ukraine would be placed under the command of General Aleksandr Dvornikov, and some units withdrawn from northern Ukraine were subsequently redeployed to the Donbas. On 19 April, Russia launched a renewed attack across a 500 kilometres (300 mi) long front extending from Kharkiv to Donetsk and Luhansk, with simultaneous missile attacks directed at Kyiv in the north and Lviv in western Ukraine. By 13 May, Russian forces near Kharkiv had withdrawn following a Ukrainian counter-offensive. By 20 May, Mariupol fell to Russian troops following a prolonged siege of the Azovstal steel works.
