An invasion is a military offensive of combatants of one geopolitical entity, usually in large numbers, entering territory controlled by another similar entity. Generally, invasions have objectives of conquering, liberating or reestablishing control or authority over a territory; forcing the partition of a country; altering the established government or gaining concessions from said government; or a combination thereof. An invasion can be the cause of a war, be a part of a larger strategy to end a war, or it can constitute an entire war in itself. Due to the large scale of the operations associated with invasions, they are usually strategic in planning and execution. Not every military offense with the goal to capture territory or remove a government is an invasion.

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.