Complex sentence: By the same token no Darius the Mede is known to history: the actual conqueror of Babylon in 539 BCE was the Persian general Gorbryas on behalf of his master Cyrus.
Split into simpler sentences: By the same token no Darius the Mede is known to history. The actual conqueror of Babylon in 539 BCE was the Persian general Gorbryas, acting on behalf of his master Cyrus.