Frontier Worlds

From Gineipaedia, the Legend of Galactic Heroes wiki

The frontier worlds were planets colonized by the Galactic Federation during the Golden Age of Humanity. Located in the galactic rim (and also possibly in the galactic core), the frontier worlds were initially a lawless region. Interstellar piracy in the frontier eventually became so bad that colonization and exploration of the region was discouraged, prompting the Federation to form a Space Armada to defend the new colony worlds from the Space Pirates in what would become known as the Pirate Wars. (LOGH: 'Julian's Journey, Mankind's Journey')