U.S. military planners call it "the red envelope." Shaped like a triangular flap, the 10,000-sq.-mi. zone encompasses the industrial heartland of North Viet Nam (see map). Yet, as though sealed off by an invisible cordon, its cluster of strategic installations around Hanoi and Haiphong has hardly been grazed by the war, for the U.S. has proscribed bombing raids on the triangleĀsave for some Soviet SAM missile sites and a few minor targetsĀever since its day-in, day-out raids against the North began last February.
Pentagon analysts, who color the inviolate area red on their...