It depends what you mean. On Installation 5 (The Halo Ring featured in Halo 2) the Elites (and some Hunters, or Lekogolo) join the Miranda Keyes and Sergeant Avery Johnson. After they deactivate the ring, putting it on standby, Keyes, Johnson and The Arbiter learn that the Prophet Of Truth is heading for Earth. John-117 (The Master Chief) is stowed away aboard the Prophet's ship. Once Keyes, Johnson and the Arbiter reach earth, they search for John-117 who crashed through the atmosphere on a piece of Truth's ship. Once he is found, they all team up to find and kill Truth before he activates all the halo rings from the Ark.