From Halopedia, the Halo wiki
At least three uprisings have been staged by insurrectionists on the planet Mamore. The United Nations Space Command was unable to prevent the first of these uprisings, a bombing attack that left millions dead. However, UNSC forces were successful in quelling the two later insurrections, which were armed conflicts rather than bombings.
On February 23, 2511, a member of the Freedom and Liberation Party detonated a commercial nuclear device, typically used for mining asteroids, in the Haven arcology. This bombing attack killed two million people and wounded 8.3 million. Millions more were expected to die due to cancers and other diseases caused by the radioactive fallout; the fallout was also predicted to cause birth defects for generations afterwards.
In late 2536 or early to mid 2537, an armed conflict erupted between insurrectionists and UNSC forces on Mamore. SPARTAN-III Alpha Company was deployed to quell the insurrection. After an unknown amount of time, the UNSC emerged victorious.
In May 2552, another insurrection occurred on Mamore. On May 10, SPARTAN-B312 took part in counter-insurgency operations on the planet, exhibiting superb skill in piloting the YSS-1000 Sabre interceptor. The Spartan's performance impressed Colonel Urban Holland of the UNSC Army's Special Warfare Command, prompting him to request the Spartan's transfer to Noble Team.
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