How do you recruit a soldier in halo reach?

Answer 1

In Halo: Reach, you cannot "recruit" a soldier, per se, but you can create a fireteam in Campaign mode. During the mission "Winter Contingency, once you arrive inside the ONI Sword Base atrium, one of the Noble squad members suggests you take a group of Marines up to help another Noble member secure an area. All you need to do after this point is walk close enough to a Marine that he/she notices you, and an indicator will appear above their head, indicating that they are a member of your fireteam.