- Main article: Halo: Reach
How to Obtain: Invasion is a gametype in which you are either the Spartans or Elites, and attacking or defending multiple areas. There are three phases found in a game. At the end of each game, the attacking team gets a score based on how far/how many points your team has taken over. Either attacking or defending:
Attacking - Gain as many points as you can. Defending - Stop the attacking team from gaining points.In order to get this Achievement you must be defending, and stop the attacking team from getting past the first Phase. The first Phase lasts 4 Minutes.
In Depth Explanation.