On 24 February 2022, Russia invaded Ukraine in a major escalation of the Russo-Ukrainian War, which had started in 2014. The invasion, the largest and deadliest conflict in Europe since World War II, has caused hundreds of thousands of military casualties and tens of thousands of Ukrainian civilian casualties. As of 2025, Russian troops occupy about 20% of Ukraine. From a population of 41 million, 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.