On 24 February 2022, Russia invaded Ukraine in an escalation of the Russo-Ukrainian War which began in 2014. The invasion has been described as the biggest attack on a European country since the Second World War and has killed tens of thousands of people on both sides. Russian forces have been responsible for mass civilian casualties and for torturing captured Ukrainian soldiers. By April 2023, about 8 million Ukrainians had been internally displaced. More than 8.2 million had fled the country by May 2023, becoming Europe's largest refugee crisis since World War II. Extensive environmental damage caused by the war, widely described as ecocide, contributed to food crises worldwide. Before the invasion, Russian troops massed near Ukraine's borders as Russian officials denied any plans to attack. Russian president Vladimir Putin announced a "special military operation" to support the Russian-backed breakaway republics of Donetsk and Luhansk, whose paramilitary forces had been fighting Ukraine in the Donbas conflict since 2014. Putin espoused irredentist views, challenged Ukraine's right to exist, and falsely claimed that Ukraine was governed by neo-Nazis persecuting the Russian minority. He claimed the goal was to "demilitarize" and "denazify" Ukraine. Russian air strikes and a ground invasion launched at a northern front from Belarus towards Kyiv, a north-eastern front towards Kharkiv, a southern front from Crimea, and a south-eastern front from the Donbas. In response, Ukraine enacted martial law and ordered a general mobilization. Russian troops retreated from the northern front by April 2022 after encountering logistical challenges and stiff Ukrainian resistance. On the southern and southeastern fronts, Russia captured Kherson in March and Mariupol in May after a destructive siege. In April, Russia launched a renewed offensive in the Donbas. Russian forces continued to bomb military and civilian targets far from the front line, including the energy grid through the winter. In late 2022, Ukraine launched counteroffensives in the south and east. Soon after, Russia announced the illegal annexation of four partly-occupied regions. In November, Ukraine retook parts of Kherson Oblast, including the city of Kherson itself. In June 2023, Ukraine launched another counteroffensive in the southeast. The invasion has been met with international condemnation. The United Nations General Assembly passed a resolution condemning the invasion and demanding a full Russian withdrawal in March 2022. The International Court of Justice ordered Russia to suspend military operations and the Council of Europe expelled Russia from its organization. Many countries imposed sanctions on Russia and its ally Belarus, and provided humanitarian and military aid to Ukraine. Protests occurred around the world, with anti-war protesters in Russia subject to mass arrests and increased media censorship. Over 1,000 companies left Russia and Belarus in response to the invasion. The International Criminal Court (ICC) opened an investigation into possible crimes against humanity, war crimes, abduction of children, and genocide, issuing an arrest warrant for Putin in March 2023.