The U.S. military's battle plan for Iraq began as "a what-if session over beers among a handful of Army majors nearly 17 months ago," the National Journal reports in a must-read article.

They were all students at the Army's School for Advanced Military Studies, known colloquially as SAMS, at Fort Leavenworth, Kan., where the Army's most promising planners take a graduate course in strategic campaigns. The young majors brainstormed about a march on Baghdad to dispose of Saddam Hussein. In its earliest versions, the plan envisioned a 125-day campaign by a U.S. force nearly twice the size of that now in Iraq.

Maj. Kevin Marcus, a SAMS graduate now attached to V Corps headquarters, helped develop the plan from a back-of-an-envelope exercise into a PowerPoint presentation that within days of being finished ended up on the desk of the president of the United States. Though any military campaign plan of the size of Iraqi Freedom has many midwivesóand for this one, they include Defense Secretary Donald Rumsfeld himself, who prodded planners to think outside the boxóMarcus saw it develop from infancy to fruition.

From the very beginning, he says, the need to synchronize a rapid, combined-arms campaign to seize the initiative with "shock and awe"óroughly the modern-day equivalent of armored blitzkrieg warfareóleapt out at planners determined to limit the opportunity for Iraqi forces to employ chemical weapons, wreak environmental havoc, or organize a coordinated defense. In bullfighter parlance, they wanted to go for a quick kill before the bull learned the trick of the cape...

Changes to Marcus' plan may have undermined its effectiveness, however.

Right up until the launch of the war, the plan kept changing... Just days before the war began, U.S. commanders had also seriously considered changing the battle plan to allow for a strategic pause at the key southern crossroads city of An Nasiriya. Such a pause would give U.S. forces time to accept the expected surrender of the 11th Division of the regular Iraqi army that defends that city, and give Republican Guard forces near Baghdad an opportunity to capitulate as well. The plan was dropped at the last minute...

By far the most dramatic and disruptive change to the battle plan, however, was Rumsfeld's decision last November to slash Central Command's request for forces. This single decision essentially cut the size of the anticipated assault force in half in the final stages of planning, and it had a ripple effect on Central Command and Army planning that continues to color operations to this day.

Notably, the Pentagon scrapped the Time Phased Force Deployment Data, or "TipFid," by which regional commanders would identify forces needed for a specific campaign, and the individual armed services would manage their deployments by order of priority. The result has meant that even as Central Command chief Gen. Tommy Franks was launching the war, forces identified for the fight continued to pour off ships in Kuwait, and not necessarily in the order of first priority.