You should read The Fall of Reach because the back story is way too deep to explain in a single forum post but I'll try and sum it up for you.

The insurrectionists also called innies are a very powerful rebel group that are trying to break away from the UNSC. The two have been at war for many years before the Covenant arrive and the war is threatening to destroy all control the UNSC has on the outer colonies. The Spartans were initially created to destroy the human rebels and indeed were very effective in dealing them major defeats. Once the Covenant show up however the entire focus of the Spartan program is changed to deal with this new threat. Once it is seen how powerful the Covenant truly are ONI starts the production of the Spartan III's, cheaper, disposable versions of the Spartan II's. That is what Noble team is, a team of Spartan III's, well all except Jorge.

You should read The Fall of Reach because the back story is way too deep to explain in a single forum post but I'll try and sum it up for you.

The insurrectionists also called innies are a very powerful rebel group that are trying to break away from the UNSC. The two have been at war for many years before the Covenant arrive and the war is threatening to destroy all control the UNSC has on the outer colonies. The Spartans were initially created to destroy the human rebels and indeed were very effective in dealing them major defeats. Once the Covenant show up however the entire focus of the Spartan program is changed to deal with this new threat. Once it is seen how powerful the Covenant truly are ONI starts the production of the Spartan III's, cheaper, disposable versions of the Spartan II's. That is what Noble team is, a team of Spartan III's, well all except Jorge.

Wow, thanks for making me feel like a complete idiot. I have read The Fall of Reach and do not remember ANY of that, LOL. Perhaps a second reading is in order.