Why did Darius and Cyrus have to agree before acting in the Medo-Persian Empire?
The Medo-Persian Empire was led by two kings, Darius and Cyrus, representing Medes and Persians. Because power was shared rather than held by one absolute ruler, any military, economic, or political action required mutual agreement between the two, making decision-making harder than under a single dictator.
Les explains that the previous kingdom, Babylon, was a government of one—an absolute ruler who did not have to consult anybody. The Mede and Persian Empire that defeated Babylon, however, had two kings who came together, Darius and Cyrus, the Medes and the Persians. So before they made any military, economic, or political move, they had to agree. Les notes it is harder to get two people to agree than one.