That bright ideas, far from guaranteeing against blunders, are often their cause is illustrated by the fate of the “D. D.” (i.e., dual drive) tanks launched offshore on D-Day. Equipped to float with impermeable canvas skirts, these were to propel themselves to the beach with an ad hoc propeller and then resume normal operation. Thirty-two were launched, their skirts deployed, but in high seas and (doubtless because of fear) too far from land. Twenty-seven sank with their complete crews, a tribute to stubborn hope, for tank after tank was launched seriatim, each sinking like a stone, observed by everyone on the launching ship. The Time-Life World War II volume dealing with the invasion devotes a full-color page to the D. D. tank without in any way suggesting that something went fatally wrong. “A TANK THAT COULD SWIM” is the caption.