Alexander III of Macedon (20/21 July 356 BC – 10/11 June 323 BC), most commonly known as Alexander the Great,4 was king of the ancient Greek kingdom of Macedon.[d] He succeeded his father Philip II to the throne in 336 BC at the age of 20, and spent most of his reign conducting a lengthy military campaign throughout Asia and Egypt. By the age of 30, he had created one of the largest empires in history, stretching from Greece to northwestern India  He was undefeated in battle and is widely considered to be one of history's greatest and most successful military commanders.
 
With this authority over all Greeks he launched a pan-Hellenic invasion of the Persian Achaemenid Empirein 334 BC, and with it began a series of campaigns which lasted for ten years. Following his conquest of Asia Minor and a series of decisive battles, particularly at Issus and Gaugamela, the power of the Achaemenid Empire was broken. He subsequently overthrew Darius III and conquered the Achaemenid Empire in its entirety.  After the fall of Persia, the Macedonian Empire held a vast swath of territory between the Adriatic Sea and the Indus River. Alexander endeavored to reach the "ends of the world and the Great Outer Sea" and invaded India in 326 BC, achieving an important victory over Porus, an ancient Indian king of present-day Punjab, at the Battle of the Hydaspes. Facing mutiny from troops, he was eventually forced to turn back at the Beas River, and later died in 323 BC in Babylon, Mesopotamia, the city which he had planned to make the capital of his empire, while on his return to Greece. Alexander's death put an end to his planned invasion of Arabia.