Reach is kinda screwed

The trailer wastes no time jumping into what’s likely to be one of the main events of the new season: The near destruction of the planet Reach, the planet home to some of the UNSC’s most essential military assets.
Reach’s fate was explored thoroughly in The Fall of Reach novel that shipped shortly before Halo: Combat Evolved in 2001, and then the 2010 prequel game Halo: Reach.