In 1948 thermonuclear weapons did not yet exist. The bombs dropped on Japan in 1945 were about 1000 times as powerful as the largest conventional bombs. Thermo

In 1948 thermonuclear weapons did not yet exist. The bombs dropped on Japan in 1945 were about 1000 times as powerful as the largest conventional bombs. Thermonuclear weapons came about in the 1950s. The thermonuclear bombs the USA and USSR had in 1958 were about 1000 times as powerful as the 1945 bombs. It was the development of thermonuclear bombs that made nuclear weaponry the swords of civilizational extinction. C.S. Lewis was writing about weapons 1000 times less powerful than you're thinking of. He was also writing when the number of nuclear weapons that had been stockpiled was much smaller.