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.