Alexander the Great conquered Persian-controlled Egypt in 332 BC during his campaigns against the Achaemenid Empire. After Alexander's death in 323 BC, his empire quickly unraveled amid competing claims by the "diadochi", his closest friends and companions. Ptolemy, a Macedonian who was one of Alexander's most trusted generals and confidants, won control of Egypt from his rivals and declared himself pharaoh. Alexandria, a Greek "polis" founded by Alexander, became the capital city and a major center of Greek culture, learning, and trade for the next several centuries. Following the Syrian Wars with the Seleucid Empire, a rival Hellenistic state, the Ptolemaic Kingdom expanded its territory to include eastern Libya, the Sinai, and northern Nubia.