History's greatest empires covered a fifth of the world, ruled hundreds of millions of people, and lasted anywhere from 100 years to over a millennium.
Empire, which comes from the Latin "imperare" meaning "to command," is a collection of states or ethnic groups united under one ruler or oligarchy.
It is a term that has been used to describe recent US foreign policy. Wrote filmmaker Oliver Stone and historian Peter Kuznick in a recent USA Today op-ed: "Obama is about to enter his second term as heir of George W. Bush's imperial strategy unless his latest foreign policy appointments signal significant change."
Each empire seemed unstoppable for an age, but in the end they were all consigned to history.
`The Portuguese Empire reached 4 million square miles at its height in 1815.
Data compiled at Wikipedia.
The Abbasid Caliphate covered 4.29 million square miles at its height in 850.
Data compiled at Wikipedia.
The French Colonial Empire covered 5 million square miles at its peak in 1938.
Data compiled at Wikipedia.
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