Albert Einstein said that in World War III, I didn't know what weapons to use, but in World War IV, I would use sticks and fists. Because World War III may be a nuclear war. Once a nuclear war breaks out, human civilization may be interrupted. Once interrupted, human evolution will come again, and then war may be sticks and fists. The severity of nuclear war is beyond our imagination, and it may spread to the universe, so every country will not break out easily.