The Invasion of the Unknown Regions was a campaign undertaken by the Rakatan Empire shortly after it's formation in 42 ABY. After the tribes of Lehon were unified in the Rakatan Unification War, the Empire decided to conquer the wilds of the Unknown Regions. It was partially successful, though the Chiss Empire and other civilizations were defeated and enslaved, the Empire of the Hand under Grand Admiral Thrawn managed to hold them off. Thrawn did not realize the threat and failed to report on it before his death at Bilbringi at the hands of the New Republic, meaning no one found out about the resurgent Rakatans.