"Who could have foreseen the breaches in the levee?"

I wouldn't think much of a unit commander who allowed for a single line of defense. I would be nervous doing structure entry with only an attack line and no exposure line. Reminds me of a line in the flick "Armegeddon" (paraphrased): 'Doesn't it make you feel safe to be blasting off into space riding a rocket that has 11,341 moving parts and carries fifteen tons of fuel and a nuclear warhead--all built by the lowest bidder?