DeeKay please explain the whole thing as the last ep left me alittle confused. Is cheif suposed to be mateys brother or something?
Nope not his brother lol. His brother died.
The Spartans, including Master Chief were 'recruited' when they were just kids. It's a bit f*cked up how the UNSC did it. The jist of it is, they are identified as being "special", like intelligent, or super fast etc, then they are kidnapped and put to training. Soon after, they are put in to a procedure that modifies their bodies. A lot of them die at this stage. Those with good brains become smart AI's if they die.
The whole of Forward Unto Dawn was Lasky remembering how he met Master Chief, and how he saved his life. Old Lasky (right at the end of episode 5 and also right at the start of episode 1) receives Cortanas emergency beacon requesting help. She says 'Sierra 117' which is Master Chiefs identifier. Then he flashes back to how he first met chief. At the end of episode 5, he's on his way to save chief, as chief saved him when he was only a recruit.
As you saw at the end of episode 5, the Spartans are just teenagers at this stage. But they're different, you see it in their eyes.
If you read the books, you know about the female Spartan 'Kelly', she's super fast.
I hope this helps lol, and more questions just ask.