From Halopedia, the Halo wiki
After the Human-Covenant War, the United Nations Space Command discovered the planet and used it as a home for millions of human refugees. Some of these refugees came from New Mombasa. The UNSC Navy maintained a presence on the planet, using it as a staging ground for a number of highly classified military exercises, including Operation: DAYBREAK, located in the highlands of Saviron. Operation: WHITE VAN also took place on the planet.
Conflict on Oban
On July 16, 2558, the planet was attacked by Jul 'Mdama's Covenant and his Promethean allies. The attack was advocated by Doctor Catherine Halsey, who believed that a bold move would attract UNSC Infinity. As Halsey predicted, Infinity was deployed to the planet and Commander Sarah Palmer led a joint Spartan-UNSC Marine operation in response to the attack. The UNSC eventually repelled the attack, and only minor damage was inflicted upon a new power station halting the colonization of the planet. However, Jul's Covenant attacked Oban just to lead Infinity into a trap.
On October 17, 2558, a Forerunner Guardian on Oban was activated and sent to Genesis by the Created, inadvertently taking a UNSC Marine patrol along with it. Oban, along with Conrad's Point, Ursa IV, Queen Anne VI, and Adelaide, was one of the first five colonies in a 72 hour period that saw such an event. The Guardian's activation caused widespread destruction and numerous causalities on the planet.
It is likely the planet is named after the Scottish town Oban.
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