Cyrus II, also known as Cyrus the Great, was King of Persia from 559 to 529 BC. He was widely considered one of the most successful Persian rulers and the founder of the Achaemenid Empire, which ruled over much of Western Asia and Egypt for many years. Cyrus succeeded his father Smerdis in 553 BC and immediately began a series of military campaigns to expand the Persian Empire. The empire grew to its greatest extent under his rule, spanning approximately 828,000 square kilometers (320,000 sq mi)
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In 529 BC he conquered Babylon and made many reforms in Mesopotamia and Egypt. His campaigns led to the demise of the Neo-Babylonian Empire and he seized the assets of the temples in Babylon, including that of Bel. Cyrus' forces defeated the Lydians and other tribes in 547 BC at the Battle of Dardanelles and made Thrace subject to the Persian Empire.
Cyrus came into conflict with Greek city-states and founded the Achaemenid empire after conquering most of coastal Anatolia. The spread of Greek culture saw his empire become one of the world's largest empires for several centuries.