On 24 February 2022, Russia invaded Ukraine in an escalation of the Russo-Ukrainian War that started in 2014. The invasion became the largest attack on a European country since World War II. It is estimated to have caused tens of thousands of Ukrainian civilian casualties and hundreds of thousands of military casualties. By June 2022, Russian troops occupied about 20% of Ukrainian territory. From a population of 41 million in January 2022, about 8 million Ukrainians had been internally displaced and more than 8.2 million had fled the country by April 2023, creating Europe's largest refugee crisis since World War II. Extensive environmental damage caused by the war, widely described as an ecocide, contributed to food crises worldwide.