Alexander, the son of the Macedonian king Philip II, was born in Pella, the ancient capital of Macedonia (Macedon). His early years were spent under the tutelage of the Grek philosopher Aristotle.
In 336 B.C., Philip was assassinated, and Alexander, then 20 years old, assumed the throne. After consolidating his rule over the Greek states, he undertook, in 334, a military campaign against the Persian Empire to the east. Alexander’s army, about 35,000 strong (although some sources say 65,000), crossed the Hellespont (the Dardanelles) from Greece into what is now Turkey and defeated a Persian force under Darius III at the Granicus River. He proceeded along the east shore of the MEDITERRANEAN SEA, then inland into Asia Minor, conquering all the territory as far as present-day Ankara, Turkey.
Alexander and his army continued southward into present- day Lebanon where he captured the Phoenician city of Tyre. Then, in 332, he headed west along the northern coast of the Sinai Peninsula into Egypt, which he conquered with little resistance. That same year, he established Alexandria on Egypt’s northern Mediterranean shore.
In 331, Alexander’s army crossed into Syria and soon reached the Tigris and Euphrates Rivers. At the battle of Gaugamela in what is now northern Iraq, he decisively defeated the Persians. Alexander pushed northeastward across present-day Iran in pursuit of the Persian army. South of the Caspian Sea, he crossed the Elburz Mountains by way of a pass known as the Caspian Gates, or the Sirdar Pass. Following the south coast of the Caspian Sea, he led his army across northern Iran to the Gurgan River. From there he headed south and east, entering what is now Afghanistan. En route, he established Alexandria in Ariis (modern Herat, Afghanistan) and Alexandria Arachosia (near modern Kandahar, Afghanistan).
Turning northeast in 329, Alexander and his victorious army entered the Kabul Valley. At the foot of the Hindu Kush range, which he believed to be part of the Caucasus Mountains, he founded the city of Alexandria ad Caucasum. Still in pursuit of the Persians, he crossed the Hindu Kush, probably by way of 11,650-foot-high Khawak Pass, and entered what is now Uzbekistan.
In the southern Russian steppes, Alexander crossed north and east to the Amu Darya, then known as the Oxus River, and conquered the ancient cities of Balkh and Samarkand. He continued northeastward as far as the Syr Darya River (known in ancient times as the Jaxartes), where he established Alexandria Eschate, the site of what became Leninabad. This settlement was the farthest eastern reach of Alexander’s travels.
From Alexandria Eschate, Alexander and his forces moved south across Afghanistan and, in 327, recrossed the Hindu Kush into India, reaching the INDUS RIVER. He led his army across the Indus to the Jhelum River (the ancient Hydaspes) and reached the Beas River (the ancient Hyphasis). Although his army defeated the Indian forces on the Jhelum, his men refused to proceed, fearing the unknown lands to the east. Alexander had planned to conquer the rest of India, as far as the GANGES RIVER, but with his troops on the verge of mutiny, he decided to return west. After having a fleet of 200 ships built on the Jhelum, Alexander led his army down the river in autumn 325. They reached the Indus and descended to its mouth in the Arabian Sea near present-day Karachi, Pakistan. Alexander sent part of his army aboard 150 ships, under the command of NEARCHUS, on an expedition westward along the coast of the Arabian Sea as far as the mouths of the Tigris and Euphrates Rivers at the head of the Persian Gulf. He led the rest of his army through the desert region of southern Baluchistan back to the Mesopotamian cities of Susa and Babylon. The overland journey was fraught with hardship; it is estimated that Alexander lost thousands of his men to thirst. Moreover, thousands of the camp followers were drowned in desert flash floods.
By 324, Alexander had returned to Persia and undertook explorations of the Tigris River into what is now Iraq. He planned to undertake a seaward exploration around the Arabian Peninsula and may have intended a circumnavigation of Africa. Before he could embark, however, he contracted a fever, probably resulting from malaria, following a 10-day drinking bout, and died in June 323 B.C. Soon afterward, his empire fell into disarray.
Alexander the Great, as he was known after his unprecedented conquest of the Middle East and central Asia, extended European geographic knowledge as far as India. His army traversed 20,000 miles of territory in Europe, Africa, and Asia, including many regions unknown to the Greeks and other Mediterranean civilizations. Traveling with his army were scientists, who sent back to Greece samples of newly discovered plants and animals. In addition, his forces were accompanied by bematists, early surveyors who measured his route. Subsequent accounts of Alexander’s conquests provided the Hellenistic world with a knowledge of Asia and led to increased contact with India and China. His route across modern Iran, south of the Caspian Sea, became a vital link in the Silk Road, an important trade route in ancient times between China and the eastern Mediterranean.