Not really that vulnerable. And despite what you hear in the media, whatever resistance there was was planned for, it just took a slightly different shape. And when you execute a supply line, you plan for X-% of loss - or "shrinkage." It's just the cost of doing bidness. Our shrinkage turned out to be far lower than that allowed for in the Plan.
Franks figgered the long supply lines would not be a problem if our men and women in the field and in the air simply did their jobs. Our men and women in the field and in the air DID do their jobs - and Franks was right. When you construct a Plan, you work within the known capabilities of your assets. In Franks' case, he knew very well what his forces were capable of, and he knew the quality of leadership in the field. Which is what turned what some might call a "daring" plan into one with plenty of margin to succeed.
And it succeeded easily.
Michael
I don't argue with anything you said. But it doesn't change my point that the supply lines were vulnerable - definitely more vulnerable than had we advanced at a slower clip.