As part of their Guide to NFL Defenses segment, here is a great read from the NYT about the evolution of the 4-3 Defense, and the history of the scheme that the Giants currently employ.
Clipped from: fifthdown.blogs.nytimes.com (share this clip)
"It didn’t take Giants Coach Steve Owen long to scheme a way to stiffen the middle of his defensive front while still pressuring the short passing lanes that Brown favored for his timing routes. Owen’s scheme came to be known as the “Umbrella” defense, and it led to the second major schematic change – the four-man defensive line – needed to invent the 4-3 front. But it wasn’t Owen who taught the scheme to his teammates. It was his talented young defensive back Tom Landry."