I don't know what weapons will be used in world war three, but in world war four people will use sticks and stones.

I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones.

I do not know how the third world war will be fought, but I can tell you what they will use in the fourth... rocks."

I don't know the weapons that will be used in the Thirth World War, but in the Forth men will use wood and stones.

I don´t know the weapons that will used in the Third Great War, but in the Forth Great War men will kill each other with stones and wood clubs.

When asked how World War III would be fought, Einstein replied that he didn't know. But he knew how World War IV would be fought: With sticks and stones!