- last post: 01.01.0001 12:00 AM PDT
Just look at the footage: the Covenant have activated the Arc, so Cortana's speech is referring to what will happen if John doesn't succeed in stopping them, i.e. what will happen if you fail your mission during Halo 3. The Arc is the master Halo ring and was built by the forerunners as a last resort against the floof, and is being fired at the end of the "announcement" trailer! So this is what Cortana refers to as "I know your past (halo 1 and 2), your future (the trailer)".