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!

So long as there are men there will be wars

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

So long as there are men there will be wars. So long as there are men there will be wars.