The Invasion of Earth was an attempt by the monitor of Installation 00 to harvest the Earth for resources to repair the Ark when the Portal at Voi was reopened in March of 2555. Because the Ark was so damaged, and the monitor blamed humanity due to the firing of Installation 08 at the end of the Battle for Installation 00, he set a countdown timer on the Halo array, knowing they would fear the firing of the array and rush to reopen the Portal. The UNSC, with the help of the Swords of Sanghelios, did manage to open the portal, and when it was opened, the monitor immediately sent sentinels to Earth, starting a large-scale battle that took a large toll on the Home Fleet at Earth. Though small and relatively easy to defeat, the monitors overwhelmed the UNSC ships on Earth, and quickly managed to destroy nearly a dozen UNSC ships, leaving only another dozen left in the battle. The battle suddenly came to an end, however, with the remaining monitors ceasing fire and retreating into the portal, due to the actions of the members of Operation: FAR STORM, who were on the Ark attempting to stop the countdown of the Halo array. In all, the attack caused significant losses to the UNSC Home Fleet, but only localized damage to Earth.