Definition: http://en.wikipedia.org/wiki/Circular_error_probable The bombs of WWII were much less aerodynamic than the "low drag" bombs of Vietnam and later. Did that affect the accuracy of the drop? If, for example, a dozen WWII GP bombs were dropped from a stationary balloon at 20,000 ft AGL how large an area would their impacts cover? What about 30,000 ft? Since the bombs approach the "Sound Barrier"at 20K and break it from 30K does this change their accuracy? Would the "Low Drag" modern bombs be more accurate? Did the loss of accuracy due to wind shear, etc and the supersonic flight characteristics both contribute to the change to low level bombing in Japan? Yes, I'm a retired Physical Science teacher who still plays with physics for fun.