 The Covenant 's superior technology allow them to annihilate the outer human colonies within four years ; the Covenant begin to destroy the inner colonies soon thereafter . As a defensive measure , the UNSC creates the " Cole Protocol " ; human ships are prohibited from directly traveling to human worlds to avoid detection by the Covenant , and destruction of a ship 's navigation databases and artificial intelligence if threatened with capture . In 2552 , the Covenant track the UNSC ship Iroquois to the world of Reach , Earth 's most well @-@ defended colony , by a hidden transmitter . A massive Covenant fleet arrives at Reach and lays waste to much of the planet . 
