The OTA Study

The Office of Technology Assessment (1979) estimated the effects of a large-scale nuclear attack on U.S. military and economic targets. This scenario assumes a direct attack on 250 U.S. cities, with a total yield of 7,800 megatons. The most immediate effects would be the loss of millions of human lives, accompanied by similar incomprehensible levels of injuries, and the physical destruction of a high percentage of U.S. economic and industrial capacity. The full range of effects resulting from several thousand warheads - most having yields of a megaton or greater - impacting on or near U.S. cities can only be discussed in terms of uncertainty and speculation. It is estimated that 100 million to 165 million people would be killed.

Long Range Fallout Pattern Over The USA
This map shows a possible long range fallout pattern over the United States

Although this type of attack is less likely than during the Cold War, the risk of a limited nuclear strike by one of the smaller nuclear powers still remains a possibility.