506th Tank Regiment
From Halopedia, the Halo wiki
The 506th Tank Regiment is a UNSC Marine Corps armored unit [1]
Background
The 506th fought during the Second Battle of Earth, and two smaller battles at Voi and New Mombasa.
During the Battle of Mombasa they were charged with making a path to the Southern Bridge Span, despite overwhelming forces in their path. They successfully achieved their mission.