The Battle of Kamchatka was a battle between Covenant remnant forces under the leadership of Jul 'Mdama, local Promethean forces under control of Cortana, and the UNSC in the form of Spartan-IV Fireteam Osiris on the planet of Kamchatka in October 2558. The battle began when Cortana, having gained control over Forerunner facilities and forces after falling into the Domain after the events on Mantle's Approach over New Phoenix in 2557, took over the Prometheans on Kamchatka and turned them on Jul 'Mdama's forces. Jul, with the help of Dr. Catherine Halsey, had been attempting to learn Cortana's intentions and stop her from achieving her goals of awakening the Guardians. Halsey had contacted the UNSC to inform them of what she had learned, and Fireteam Osiris was sent to extract her. Osiris was able to infiltrate Jul's forces in the midst of the battle, and recovered Dr. Halsey, killing Jul 'Mdama in the process.