For their departure, Alexander had a fleet of 1,800 ships built in just two months, under the supervision of his admiral and old friend Nearchus (c. 360-c. 300 B. C.E.). Carpenters used simple tools to construct both river-
Boats and vessels that could be taken to sea. In November, Nearchus led the fleet south from the Hydaspes River toward the Indus River and the Indian Ocean.
The main part of the army marched alongside the river, at the same pace as the ships. The army, which now included elephants, had to fight hostile groups along the way. They fought with the ferocious Mallians, who lived east of the Acesines (today the Chenab) River. During one fight, Alexander received a serious wound when an arrow pierced his chest. The army reached the port town of Patala (near today’s Hyderabad) in July 325 B. C.E. After resting with his troops and exploring some nearby river channels, Alexander began to plan out his return trip to Babylon. First, he instructed a trusted general, Craterus (c. 362-321 B. C.E.), to take a more northern route west, the easiest way back. Craterus traveled with the elephants and about a third of the troops, including older or sick soldiers.
At the same time, Nearchus and nearly 20,000 men set sail west from the mouth of the Indus River, up the coast into the Persian Gulf. They explored the northern shore of the Arabian Sea and the Persian Gulf, seeking the mouth of the Tigris and Euphrates Rivers. Today it is not easy to reconstruct their voyage, as it was not possible at that time to measure distances at sea. Many historians believe the fleet traveled this route to open up a sea trade route between Persia and India. To accomplish this, they would have had to chart the coast and make maps of landing sites and wells. In fact, trading routes did open up or were reinforced after this voyage. One important trade route linked western India to port cities of Egypt via the Red Sea.