1 Alpha (Earth-2042)

1 Alpha was a Systems Alliance Army unit stationed on Reach during the Clone Wars. During the Fall of Reach, they fought in the Siege of New Alexandria, where 1 Alpha 3 and her team became pinned down by CIS fire on a rooftop in New Alexandria. However, SPARTAN-B312 was able to relieve them.

Source

 * https://www.halopedia.org/1_Alpha