Battle of Kamchatka

Operation: ANCHORITE was an engagement fought between the forces of the United Nations Space Command, Jul 'Mdama's Covenant faction, and the Prometheans in 2558, during which Dr. Catherine Halsey was rescued and Jul 'Mdama was assassinated.

Prelude
Before the Great Purification, Kamchatka was an astroengineered Forerunner world, created to serve as a link to the galaxy-spanning network the Domain.

In 2558, a long-dead communications hub on the planet's surface activated, attracting the attention of Jul 'Mdama's Covenant faction. The Covenant established an outpost while Dr. Halsey, under temporary alliance with Covenant leader Jul 'Mdama, studied the relay and discovered that her old AI Cortana was alive and responsible for recent attacks on the human colonies by awakening Guardians. She contacted the UNSC about her discovery, but they did not take any action for three weeks. In the meantime Halsey made unsuccessful attempts to contact or deter Cortana's transmissions, but her lack of headway led to Jul 'Mdama growing impatient with her.

Battle
In October 2558, the deployed Fireteam Osiris, a Spartan-IV special operations squad, to retrieve Halsey and assassinate Jul 'Mdama. They dropped from low orbit by Pelican and landed amidst an enormous ship and ground battle, as Cortana had taken control of Jul's Prometheans and was unleashing them against him. The Covenant made little headway against the numerous droids, with the constructs managing to bring down a blockade runner and force back a Kraken walker. The chaos from the Prometheans' rebellion provided Osiris cover from the Covenant, allowing them to sneak to the temple where 'Mdama and Halsey were stationed.

After reaching the temple, Osiris killed Jul's Zealot guards and then turned to Jul himself, who was killed attempting to fight off Spartan Jameson Locke. They then took custody of Dr. Halsey and she was brought back to the Infinity to aid the search for the Guardians.

Aftermath
With Jul 'Mdama dead and the Prometheans now against them, his Covenant troops became desperate. Some of them fled to the Argent Moon to retrieve their soldiers scavenging the station, though most of them were killed during the raid on Argent Moon. Most of the rest regrouped on Sanghelios, attempting an attack on the Vadam clan burial grounds in hopes of a revenge attack against the Arbiter.

Trivia
Halo Waypoint's Canon Fodder article Fifty Caliber states that "unconfirmed reports" about the Battle of Kamchatka claim there might have been a temporary alliance between Fireteam Osiris and the Sangheili Kitun 'Arach of Jul's forces. This is a reference to the Enemy of my Enemy achievement, in which the player(s) can choose to save a Sangheili Warrior assaulting a hill against Promethean Soldiers, turning him from an enemy to an ally.

List of appearances

 * Halo 5: Guardians
 * Halo: Legacy of Onyx
 * Halo: Bad Blood