In the last five or six thousand years, empires one after another have arisen, waxed powerful by wars of conquest, and fallen by internal revolution or attack from without.

Empires won by conquest have always fallen either by revolt within or by defeat by a rival.

When the Industrial Revolution of the nineteenth century brought a rapid increase in wealth, the demand of workers for a fair share of the wealth they were creating was conceded only after riots and strikes.

Our civilization is now in the transition stage between the age of warring empires and a new age of world unity and peace.

Some wars have been due to the lust of rulers for power and glory, or to revenge to wipe out the humiliation of a former defeat.

Science has produced such powerful weapons that in a war between great powers there would be neither victor nor vanquished. Both would be overwhelmed in destruction.