G617 g1

G617 g1, located in the G617 System, was the location of the Milky Ways first infestation by the Flood xenoform. The Forerunners first sent a Primary Pioneer Group to investigate the ecosystem of the planet. When that team disappeared, they sent the Advance Survey Team-Alpha, which also disappeared. After that, they sent a "medium intensity military exploratory detachment" to engage this new threat: this began the Flood-Forerunner War.

Trivia

 * This is similar to the beginning of the Human-Covenant War, as two groups of ships were sent to investigate when the Covenant glassed Harvest.