Type of military offensive where armed forces of one geopolitical entity forcibly enter another
An invasion is a military offensive of combatants of one geopolitical entity, usually in large numbers, entering territory controlled by another similar entity, often involving acts of aggression. . 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.
https://en.wikipedia.org/wiki/Invasion