What makes a Great Defense!
After researching this topic for many years...well, not ready researching...but Heavy debate over the water cooler... it seems to me that a few things need to be in place before a defense can be considered "The Greatest Defense of All time".
 1. Longevity 2. the Numbers 3. Intimidation! [domination too]

It's Very clear that the Steelers "Steel Curtain" Defense of the 1970's had ALL the above elements. No one wanted to enter 3 Rivers Stadium back in the mid to late 70's. No-one! This unit put together a defensive run that has landed over 4 members in Pro Footballs Hall of Fame.  - Jack Lambert, Mean Joe Green, Mel Blount and Jack Ham! On top of all of that, they have the Rings to prove their greatness. 4 Super Bowls in 6 years. a Feat that has Not been dubbed since! The Steel Curtain is # 1 in our book.

 Wait a second now!
The Chicago Bears 1984-85-86 teams brought a Defense to the table that has rivaled the Steel Curtain's dominates of the record books as being the greatest defense ever. If you had the chance to witness this Out-right DOMINATING Bears 46 Defense of 1985, you probably witnessed the most feared defense to ever line up against an opponent. When watching the 1985 Super Bowl between the Patriots and Bears... I really felt that the Bears could hold the Pats to less than positive yardage. Whether playing the pass or run, the Bears 46 Crushed the Patriots. period. Side note: The Curtain shut down the Vikings in Super Bowl IX like lock down time in the state pen's... but not like the Bears did the Pats. Pure Dominates!

Which begs the question...who's the Greatest?
you be the judge, submit: bears 46 | Steel Curtain
The Fans are listening!  55% to  45% Da Bears!

So who made up the "Steel Curtain"?
a question that always seems to be asked, yet no-one can answer in a single try. The Steel Curtain was more of an era in Pittsburgh Defense and Not just a certain set of players. However, over the years...Joe Green, Jack Lambert, Jack Ham and LC Greenwood have become the "core" members of that Steel Curtain Defense. Although, some will debate that the Steel Curtain refers to the 4 members of the D-line Only!: Joe Green, LC Greenwood, Dwight White and Ernie Holmes.
Nevertheless, how ever you slice it...this unit made up a defense that will live forever in the NFL's history books!

 

Found on the web:
Someone emailed me this list of the greatest defenses. You be the judge. Was any team left out? Submit yours!

1. Steel Curtain: Blount, Greene, Jack Ham and Jack Lambert are all in the Hall of Fame. The Steelers just embarrassed good competition.

2. 1985 Bears: A force of nature. Buddy Ryan's aggressive, 46 scheme changed the game of football.

3. Purple People Eaters: Led by Alan Page, Carl Eller and Jim Marshall, the Vikings had the best front four in the history of football.

4. Doomsday Defense: Coolest nickname and an outstanding front in White, Too Tall Jones and Harvey Martin. This defense produced four fumble recoveries and four interceptions in Super Bowl XII.

5. No-Name Defense: Very similar to the Ravens. Strong up the middle with linebacker Nick Buoniconti and safety Jake Scott, both of whom played great in Super Bowls.

Link: Best Sports Nicknames. [The Curtain makes the list]
Link: CBS Sportsline "Steel Curtain" write-up
Link: Ravens' defense doing nice impersonation of Steel Curtain
LINK: The 46 Defense! Sportsline.com
 

Wow! what the 1970's spawned in sports:
 1979 Pittsburgh Super Bowl Champions SB 14
 1978 Pittsburgh Super Bowl Champions SB 13
 1975 Pittsburgh Super Bowl Champions SB 10
 1974 Pittsburgh Super Bowl Champions: SB 9
 1971 Mr. Hockey " Gordie Howe" retires
 1971 Pelé has 3 dazzling years with NYComos
 1972 Seven for Spitz, Gold that is.
 1972 NFL Greatest Play, The Immaculate Reception
 1973 The Juice breaks 2000 yards
 1973 Battle of the Sexes,..u remember Billy Jean King
 1973 Triple Crown Secretariat soars
 1974 715, Hank's historic homer
 1976 A perfect 10!, Nadia Comaneci nails it.
 1979 Bird and Magic, Greatest Finals ever!