Invasion

Invasion is a gametype in Halo: Reach Multiplayer Beta.

Overview
Invasion is team-based of six-versus-six gametype and described as a large vehicular-based firefight. The gametype is only playable on in the Beta and will be the only gametype that features vehicles. The game will begin on what is known as the Phase. As the game continues, more Phases unlock meaning there will be more objectives to be completed, vehicles will become available, and more Loadouts will become available as well.

In the beta, players will not be able to choose which multiplayer model/teams they want to play; the Beta system will automatically assign the player as either play as a SPARTAN (Defending Team) or an Elite (Attacking Team).

Phases
The default Invasion gametype is broken into three tiers; successfully completing an objective in one tier will unlock the next tier. If the Spartans can hold out during any one phase, the game is over and they score a victory. As a result, UNSC Longswords will fly overhead and clear the zone with a tactical strike, rendering any and all data stored on the core completely destroyed.

Phase 1
Phase 1 requires the Elites (Attacking Team) to shut down one of the two generators positioned inside the Commonwealth. The process of shutting down the generators requires 20 seconds. Successfully shutting down one of the generators will power down the security systems that leads to Phase 2 and the match will be extended for an additional four minutes. Failing to shut down the generators in less than four minutes allotted in Tear 1, and the Spartans (Defending Team) will win.

Phase 2
Phase 2 requires the Elites to control one of the three newly marked territories; two located inside the refinery and the third located beside the Spartan's vehicle bay. Similar to Phase 1, a total amount of 20 seconds is required to successfully shutting down the security systems. Successfully completing Phase 2 will leave the data core exposed for Phase 3 and add an additional four minutes to the match.

Phase 3
In Phase 3, the Elites must retrieve the data core and deliver it back to the Phantom hovering onto the scaffolding near the ridge. When carrying the data core, the carrier's movement will be hindered by the package, similar to that when carrying support weapons in Halo 3, and will be left defenseless and vulnerable to the Spartans. Successfully delivering the data core to the Phantom will end the game and Elites will win.

Trivia

 * There is also a variant called Invasion Slayer, which appears to be a six-versus-six Spartan-vs-Elites slayer variant. While not much is known, phases still remain and it is presumed completing objectives does not unlock points but merely furthers progress of the game itself.