You're ignoring the omnipresent friction of war. Even in the most perfectly executed strategy, there are substantial random variables. The way you win most times is by the averages. Fight in such a way as to win more often than you lose, then keep plugging past the turning point. It's either that, or the sudden appearance of a miracle weapon at the last minute.
Maybe this is the fundamental mental defect of those who get all happy about every little cluster of alliance casualties. They think if we lose anyone at all, we must have lost the whole war. No, that's not the bottom of it. The bottom of it is they're so desperate to see America and/or Dubya humiliated that they'll grasp at any straw. And they can't even bring themselves to deny it.
How about you? Would you rather see the bad guys win than see Dubya vindicated? Just checking..