Seriously studied for almost sixty years, nothing would seem better understood than the effects and terrible consequences of the use of nuclear weapons. Yet, surprisingly, for decades, one far-reaching effect--the mass fire damage caused by "firestorms"--was neither examined in depth nor widely understood. This matters because, for modern nuclear weapons, under almost all conditions and for many targets of interest, the range of devastation from mass fire substantially exceeds that of damage from blast. Once mass fire began to be studied analytically and through reanalysis of empirical experience, the quite well-developed findings were not widely accepted. There may be somewhat greater acceptance now, but, when it comes to nuclear operations, understanding by physicists is not enough. Knowledge has to be incorporated into organizational procedures, specifically, the algorithms used in strategic nuclear war planning.