From Halopedia, the Halo wiki
The Buta system, known to UNSC forces as the Agni system is a solar system located within Covenant space. The system was previously controlled as part of the Forerunner Ecumene, with many artifacts left in the system.
Prior to the Forerunner-Flood war, the Forerunners settled the Buta system on the planet Zhoist, building the Ten Cities of Edification there. Many millennia following the firing of the Halo Array, the Covenant found these ruins and leveraged technologies from them, helping the Covenant boost their space travel capabilities and weapons technology.
In 2526, the Human-Covenant War spread to the Buta system, as one of the first strikes by the UNSC into Covenant space. As part of Operation: SILENT STORM, Task Force Yama launched an Attack on Zhoist, aiming to destroy its cities and the fleet support station known as the Ring of Mighty Abundance to slow down the Covenant war machine.
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