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Russia invaded Ukraine on 24 February 2022. Internationally considered an act of aggression, the invasion has triggered Europe's largest refugee crisis since World War II, with more than 4.3 million Ukrainians leaving the country and a quarter of the population displaced.

The invasion marked a major escalation of the Russo-Ukrainian War, which began following the 2014 Ukrainian Revolution of Dignity. Russia subsequently annexed Crimea, and Russian-backed separatists seized part of the south-eastern Donbas region of Ukraine, sparking a war there. In 2021, Russia began a large military build-up along its border with Ukraine, amassing up to 190,000 troops along with their equipment. In a broadcast shortly before the invasion, Russian president Vladimir Putin espoused irredentist views, questioned Ukraine's right to statehood, and falsely accused Ukraine of being dominated by neo-Nazis who persecute the ethnic Russian minority. Putin said that the North Atlantic Treaty Organization (NATO), by expanding eastward since the early 2000s, had threatened Russia's security – a claim disputed by NATO – and demanded Ukraine be barred from ever joining the alliance. The United States and others 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 statelets in Donbas controlled by pro-Russian separatists. The following day, the Federation Council of Russia authorised the use of military force abroad, and overt Russian troops 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. In response, Ukrainian president Volodymyr Zelenskyy enacted martial law and general mobilisation.

Multi-pronged offensives were launched from Russia, Belarus, and the two occupied territories of Ukraine (Crimea and Donbas). The four major offensives are the Kyiv offensive, the Northeastern Ukraine offensive, the Eastern Ukraine offensive, and the Southern Ukraine offensive. Russian aircraft and missiles also struck western parts of Ukraine. Russian forces have approached or besieged key settlements, including Chernihiv, Kharkiv, Kherson, Kyiv, Mariupol, and Sumy, but met stiff Ukrainian resistance and experienced logistical and operational challenges that hampered their progress. Three weeks after launching the invasion, the Russian military had more success in the south, while incremental gains or stalemates elsewhere forced them into attrition warfare, resulting in mounting civilian casualties. In late March 2022, Russian forces withdrew from the Kyiv region with the declared aim to refocus on Donbas, leaving behind devastated settlements and growing evidence of atrocities against civilians.

The invasion has been widely condemned internationally. The United Nations General Assembly adopted a resolution which condemned it and demanded a full withdrawal. The International Court of Justice ordered Russia to suspend military operations and the Council of Europe expelled Russia. Many countries imposed new sanctions, which have affected the economies of Russia and the world, and provided humanitarian and military aid to Ukraine. Protests occurred around the world; those in Russia have been met with mass arrests and increased media censorship, including banning the terms "war" and "invasion". Numerous companies withdrew their products and services from Russia and Belarus, and Russian state-funded media were banned from broadcasting and removed from online platforms. The International Criminal Court opened an investigation into allegations of Russian military war crimes in Ukraine.

Material is taken from Wikipedia