What is the Cover 2 Defense?

The Cover 2 defense is a defense that relies on two guys to take roughly half the field, and act as a "safety net" in case the other team gets past the other guys on the field.

What are the origins of the 4-3 Defense?

The Cover 2 defense was created by Tony Dungy and Monte Kiffin, however they often shift credit to the 1975 Pittsburgh Steelers coaches Chuck Noll and Bud Carson for having created this defense.

Are there any famous teams who used this defense?

A version of this defense was used by the 1970's "Steel Curtain" Pittsburgh Steelers, but was made famous by Tony Dungy and the Tampa Bay Buccaneers, and followed with him to the Indianapolis Colts, who won the super bowl under Dungy in 2006.