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At the end of the Human-Covenant War, the Covenant finally discovered the location of Earth and invaded it. By November 10, 2552, the Covenant had began to excavate and occupy built-up positions centered at Free-fire area OZONE.[note 1]
On November 17, Covenant battlenet cohesion broke with the departure of the Prophet of Truth through the portal to Installation 00. UNSC forces took advantage of this windfall and began a counteroffensive across the former southwestern URNA. On November 19, UNSC flagword LUX was declared and a UEG emergency evacuation broadcast was initiated in anticipation of a tactical nuclear deployment against shielded enemy positions at OZONE, which followed shortly after. On December 3, Fleet Admiral Joseph Harper directed Operation: MARSH FLASH, which successfully eliminated clusters of high-value Jiralhanae leadership attempting to activate a Forerunner artifact there.
Attacks in Arizona
On July 25, 2557, The Ur-Didact arrived at Earth with his ship, the Mantle's Approach, and a Composer. The Didact used the Composer to target New Phoenix, Arizona, and successfully composed the entire population--approximately seven million people. John-117, who had managed to get aboard the Forerunner vessel, stopped the Didact before more damage could be done and destroyed the Mantle's Approach with a Mark 2556 MFDD HAVOK tactical nuclear weapon. The United Nations Space Command moved swiftly to establish a presence in the city, particularly in order to secure a Forerunner artifact at a local ONI facility. Soon after the city was first attacked, however, portals throughout the city opened and Jul 'Mdama's Covenant poured into it from Installation 03, along with a host of mechanical Prometheans. The enemies were repelled by the UNSC and the portals were closed when a device known as the Conduit was united with the artifact ONI had been studying. Due to uncertainty over the finality of the Didact's defeat, the UNSC Security Council decided to hide the details of the attack from the public, concealing it as an attack by only the Covenant remnants which had been stopped by the return of humanity's greatest hero, the Master Chief. Additionally, the Office of Naval Intelligence quarantined New Phoenix for a year. Six months later, however, ONI public relations officer John Sullivan released a statement to the press confirming the Covenant was not responsible for the attack.
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