Invade

Invade is a verb describing the act of entering a space or domain by force or without permission. In military usage, an invasion is a large-scale entry of armed forces into another country or territory with the aim of conquest, occupation, or overthrow. The word can also be used in non-military contexts to mean intruding into someone’s privacy or into a system, and in biology to describe the spread of a non-native organism into a new environment.

The word derives from the Latin invadere, from in- “into” and vadere “to go.” The form entered English in the medieval period and acquired its modern senses related to forceful entry and spread.

In international law, invasions qualify as acts of aggression and are generally prohibited by the UN Charter unless authorized by the UN Security Council or in legitimate self-defense. Even when not illegal, invasions raise issues of sovereignty, occupation, civilian harm, and potential war crimes. The terminology and legal status of specific actions can be contested, and interpretations may vary with context and evolving norms of international conduct.

In ecology, an invasion refers to the rapid spread of an introduced species into new habitats, often displacing native species and altering ecosystems. In everyday usage, invasion can describe unwanted intrusion into privacy, property, or digital networks, highlighting ethical and legal concerns about boundaries and consent.

Historically, notable invasions include the Norman invasion of England in 1066 and the Allied invasion of Normandy in 1944, among others. The concept remains central to discussions of sovereignty, security, environmental management, and civil rights.