I wouldn't call former Bears defensive coordinator Buddy Ryan the father of the the 46 Defense, but he certainly was one of the fathers. You could make a case that what former Atlanta Falcons defensive coordinator Jerry Glanville is the father of the 46 Defense. They just didn't call it that in Atlanta in the mid and late 1970s and even into the 1980s when Glanville was still coaching the Falcons defense before he moved on to Houston. In Atlanta this defense was called the Grits Blitz.
But what is the 46 Defense and why is it called that when the Bears didn't even line up four men up front and six right behind the defensive line. The Bears would line up four DL generally, two defensive ends and two defensive tackles. With Otis Wilson and Wilbur Marshal who were normally linebackers would line up next to either defensive end Dan Hampton or Richard Dent. With middle linebacker Mike Singletary covering the middle of the field almost by himself.
The 46 Defense to paraphrase Buddy Ryan was based off of a simple mathematic proposition. That if the offense lines seven up front and we line eight up front, at least one defender will always go unblocked and free to either rush the QB or stuff the runner. Which meant the Bears on defense would generally have eight guys lined up in the box. Not all of them on the line of scrimmage. Four down front, two linebackers again right next to one of the DE's, Mike Singletary right behind the DT's and a safety right near the line of scrimmage as well.
What also made the Bears 46 special was just because they generally lined up eight guys in the box, that didn't mean eight guys were always rushing the line of scrimmage. They wanted the offense to always believe that was a possibility and have to prepare for that. Most offenses fell for that trap and played the Bears 46 conservatively and tried to keep more guys in for protection and run blocking. Leaving fewer people in the play that the QB can throw the ball to and also making it harder to run the ball. Because instead spreading the 46 out, you leave everybody in making things very crowded.
The opposite is true in how you attack the 46. You don't go conservative especially if you are a good offensive team with a good QB and passing game. You bring in extra WR's and spread the defense out, which gives you more room to operate on offense. And once you establish the passing game and can even hit a few passes deep, now you got the Bears thinking about the passing game. Which gives you room to run the football.
As I mentioned last night, the Dolphins were the only team that figured out how to attack the Bears 46 in 1985 and have the personal to do it on offense. The Redskins studied that and used their own variation of that in 86 and 87. By using maximum protection, but not to run the football, but to hit big passes down the field. And spread the Bears out as well to throw short and that is how they beat the Bears in 86 and 87 in the NFC Playoffs. As well as being good enough on defense to stop the Bears.