Chief, can you hear me?
When I was born, seven years ago...
...I already possessed the entire sum of recorded human knowledge.
It took me almost two hours to process and understand all that information.
But I can't be sure which memories are mine or even what's true...
...what's real.
I've discovered a great deal more information since then.
For an Al, I've lived a very long time.
But now, after seven human years...
...I have finally come to understand your role...
...your place in the universe.
And how you came to be here.
The eons of human evolution...
...invention, aspiration and war.
Always war.
The oldest, most enduring of human practices.
A hundred thousand years ago...
...a great civilization existed in this universe.
Like all great civilizations...
...they faced a sudden and dire turn of events.
A threat to their primacy from outside.
Something they never expected...
...never prepared for.
A deeply alien threat they called simply the Flood.
An unstoppable force, an unquenchable thirst.
It devoured everything it touched.
At first their technology, their courage seemed like it might prevail.
But they waited too long to see the threat...
...to join the fight.
The Flood had spread too far and too wide.
It fed on intelligent life, and in doing so...
...became ever more intelligent itself.
The Flood was unique.
It used their very strength against them.
They were the Forerunners.
The Forerunners were a wise, highly intelligent, noble people.
And with a belief in justice, in peace...
...they bravely faced the adversary.
They sought to sterilize it.
I can only guess some of this...
...fill in the gaps.
But it was an impossible fight.
Realizing defeat was inevitable...
...the Forerunners made a decision to destroy everything.
Ironically, they did this in order to preserve life...
...to create a future for you, yet unborn...
...knowing they themselves would not survive.
In a desperate attempt to ensure that they would be the last victims...
...they built a secret weapon of terrifying power.
It was called Halo...
...an array of weapons scattered throughout the galaxy.
Its effect would spread throughout known space, destroying the Flood...
...and every thinking creature in the galaxy.
You see, the Flood fed on sentient species to survive.
The device would destroy the infection and its food supply.
A thousand other plans were tried, and failed.
This was the last resort. Halo.
And finally, it was over in an instant.
Every intelligent life form left in the galaxy was obliterated.
But from the ashes of apparent defeat...
...a victory.
The Forerunners had cataloged, stored and protected...
...population samples from the Halo event.
DNA, embryos, even living specimens.
In order to repopulate, restore the galaxy.
Once the galaxy was cleansed of Flood, the threat sterilized...
...they repopulated worlds...
...rebuilt that which they had torn down...
...and reseeded life.
But the Forerunners themselves were gone forever.
This destruction, this conflagration was their gift to you...
...and their sacrifice.
They left you to reclaim your world...
...to rebuild it with your own hands...
...by sacrificing themselves...
...eternally.
It seemed that life had finally found its peace.