Board Thread:General Discussion/@comment-4913740-20130707123202/@comment-4913740-20130722110728

FOXHOUND is a major development in the series because Big Boss will later use it as cover for his Outer Heaven Uprising. Not only that, but FOXHOUND are the main antagonists of MGS1, as well as a facsimile of FOXHOUND being used as the organisation Raiden is a part of in MGS2.

But in Portable Ops, it has not been created yet. In fact, Portable Ops shows the very early beginnings of FOXHOUND, as this is the first time Naked Snake is a leader and the joining of Campbell and Naked Snake will later mark the beginning of the series (Metal Gear 1).

And in Peace Walker, they're simply a special forces group. There's nothing to make the group significant, it's just a group that Big Boss led for a while and left when he split ties with Zero.