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. 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.

History

Archaeological evidence indicates that invasions have been frequent occurrences since prehistory. In antiquity, before radio communications and fast transportation, the only way for a military to ensure adequate reinforcements was to move armies as one massive force. This, by its very nature, led to the strategy of invasion. With invasion came cultural exchanges in government, religion, philosophy, and technology that shaped the development of much of the ancient world.

Before the days of package tours and cut-price airlines, military invasions functioned as a standard major form of proto-tourism – bringing large numbers of foreign visitors into new environments, with the consequential social, cultural and economic impacts on indigenous populations and on the invaders.