NFL action has escalated from ground warfare to an all-out air campaign. What Bill Walsh started with the west coast offense, Marv Levy juiced with the k-gun. Now, thanks to Dick Vermeil, it's the era of the vertical game, and anything goes.

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BILL WALSH, 49ers HEAD COACH, 1979-88
WEST COAST OFFENSE (1984)
Formation: Two RBs, two WRs, one TE
Philosophy: Timing is everything

We ran multiple formations 20% of the time. Now people are using them 70% of the time. The key to our offense was that no matter what kind of movement we used, we always started with two backs and a tight end. Either position could go in motion and be used as a receiver, but as long as we started in that formation, teams stayed in their base defense and that created mismatches. We wanted to be very detailed, very specific about the length of the steps Joe Montana took, the number of steps he took, the distance of the receiver's route, the timing of the throw and Joe's reads: when he moved from his primary receiver to an alternate; then to an outlet; then scrambled. We stretched the field sideline to sideline using short crossing patterns. That helped pick off defensive backs, so when Dwight Clark or Freddie Solomon caught the ball, they only had one defender to beat. It was up to them to make moves and get downfield after a catch. Those things just picked up the speed of the game drastically.

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	Marv picked up where Walsh left off.

MARV LEVY, BILLS HEAD COACH, 1986-97
K-GUN (1992)
Formation: Shotgun, RB, TE, three WRs
Philosophy: No-huddle keeps D guessing

If running backs are judged by average yards per touch, Thurman Thomas was a harbinger of that. He was a running threat, and as much a threat in a pattern as our receivers. You see teams using a single back today; we started that. We still ran more than we passed, though we spread the field out with multiple formations. But in a playoff game in 1990 against Cleveland, we went with the no-huddle and, although we lost, it worked well. We decided to go with it for the next season. We kept the tight end instead of another wideout so we could be a power running team if we had to be. But our base scheme was pretty consistent: Thurman would flare out as a safety valve, the TE and slot receiver ran crossing patterns underneath and our wideouts ran deep outs. Defenses couldn't substitute and get out of their base alignment. They just couldn't get complicated. That's why Thurman was always open or lined up in a mismatch. Plus, covering receivers tired out the defensive backs. Now teams use the same approach -- spread the field out, use multiple formations, wear down defenses with the pass. The passing game has turned out to be more of a percentage game than it used to be, but remember this: 75% of all turnovers happen in the passing game. You can't forget about the run.

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AL SAUNDERS, CHIEFS OFFENSIVE COORDINATOR, 2001-02
VERTICAL GAME (2002)
Formation: RB, TE split, three WRs
Philosophy: Get maximum targets upfield fast

The traditionalists will say, "Run the ball, run the ball," but the game has evolved. It's about speed, and passing is a faster way to get from one part of the field to the next. Higher risk, higher reward.

Here's a good way to explain it. Place two fingers from your left hand and three from your right on a table. Then shoot your hands straight up the table as far as they will go. That is the vertical passing game. Dick Vermeil says, "There is no West Coast offense anymore. Everybody steals and everybody is doing what everybody else is doing.

If it works, you use it." It's true. The 49ers' Two Jet Flanker Drive? For us it's 940 F Shoot.

But the basic difference is the vertical attack's philosophy that is a bit more ambitious than the West Coast's. The West Coast challenges defenses laterally, we attack the vertical seams of the field. We want to get as many targets as possible as far up the field as possible, as quickly as possible. The tight end is a first option in the West Coast. With us, he's a third-read checkdown for the quarterback after the QB looks downfield first, then works his way back to the line of scrimmage. The philosophy: never play offense defensively.

When you talk about the evolution of the passing game, you should hang your hat on one thing: Players becoming interchangeable parts. Your five skilled players on offense are much more involved in the passing game than they ever were before. Remember that wave of young, versatile quarterbacks a few years ago? It's as if the other players on offense have elevated their games to meet the standards set by the new type of quarterback. The more interchangeable the players are, the fewer limits there are on your offense.

Because of the versatility of guys like Priest Holmes and Tony Gonzalez, we can disrupt defenses with all of our different formations and personnel packages and pre-snap shifting. That's how we dictate tempo, keeping defenses on their heels. But, ultimately, it comes down to this: When you pass more you have a better chance of scoring more points, and when you score more points you have a much more entertaining product.

And really, doesn't it all come down to that?

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This article appears in the December 9 issue of ESPN The Magazine.