History has seen empires that stretch across a fifth of the world; others that ruled hundreds of millions of people; and some that lasted more than a millennium.
Each empire seemed unstoppable for an age, but they all crumbled in the end.
Indeed, the age of empires may have ended with World War II, as world powers have moved on from colonization and conquest in favor of geopolitical and commercial influence.
We've ranked the 19 greatest empires of all time by the number of square miles each had conquered at their peak.
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The Turkic Khaganate spanned 2.32 million square miles at its height in 557 until a civil war contributed to its collapse in 581.
The Han imperial dynasty spanned 2.51 million square miles at its peak in 100 B.C. It collapsed by A.D. 220 after a series of coups and revolutions.
The Ming Dynasty spanned 2.51 million square miles at its height in 1450, but economic breakdown and natural disasters contributed to its collapse in the early 17th century.
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