Definitions of invade:

• verb:   occupy in large numbers or live on a host
• verb:   march aggressively into another's territory by military force for the purposes of conquest and occupation

  Example: "Hitler invaded Poland on September 1, 1939"

• verb:   penetrate or assault, in a harmful or injurious way

  Example: "The cancer had invaded her lungs"

• verb:   to intrude upon, infringe, encroach on, violate

  Example: "This new colleague invades my territory"