Invasion
Part of speech: noun
Definition: A military action consisting of armed forces of one geopolitical entity entering territory controlled by another such entity, generally with the objective of conquering territory or altering the established government.
Example sentence: We... our war began September the 3rd 1939, with the invasion of Poland by Germany, and thereafter the great state of danger in England at that time, with the bombings, necessitated the evacuation of children.
Intrusion
Part of speech: noun
Definition: The forcible inclusion or entry of an external group or individual; the act of intruding.
Example sentence: I couldn't ever write a straight crime novel: there'd be an intrusion of weirdness at some point.