Alexander arrived with his troops at the banks of Hydapses (Jhelum). The
  river was already in spate and therefore, a halt had to be made for several
  weeks. Finally he crossed the river in dark and took Porus by surprise. A
  fierce battle was fought on the plains of the Karsi. Porus himself displayed
  unprecedented courage, but he lost the battle. About twelve thousand
  soldiers were killed and six thousand were taken prisoners. The wounded
  Porus was persuaded to surrender. The conqueror admired Porus’
  independent spirit. He not only granted Porus his own kingdom but also
  enlarged it by adding a state of larger dimension
     Alexander advanced eastwards crossing the Jhelum. He defeated the
Glansai or Glankanikoi and proceeded further. He crossed the Akesines
(Chenab) and the Hydraotes (Ravi) and annexed Sangala, the capital of the
Kathaioi (Kathas) by storm. King Sanbhuti had no option but to submit to
Alexander. Then he advanced towards the bank of the Beas with a view to
annexing the Magadha empire. But here his fatigued soldiers refused to cross
the river. Hardship of prolonged campaigns and isolation from homes had
certainly made them keen to return to their homeland. Simultaneously, they
learnt that beyond the Beas was a strong state which might not be subdued so
easily. Hence, Alexander failed to persuade his soldiers to take up the new
venture.
     Consequently Alexander ordered retreat making adequate arrangements
to look after the newly acquired possessions. He divided the whole territory
from the Indus to the Beas into three provinces and put them under the
overall charge of governors. Some part of the Macedonian army was left
behind to assist the governors to maintain law and order.
     The retreat began in October 326 BC down the Jhelum and the Indus.
However, the return journey of Alexander was not free from ordeals. Many
republican clans inhabiting southern Punjab attacked and harassed the tired
and retreating columns. Beating back and destroying the upstarts, Alexander
reached Patala at the head of the Indus delta. He divided his army into two.
One portion was dispatched by sea under the command of Nearchus. The
other was kept under his own command. In September 325 BC Alexander left
the periphery of modern Karachi by land route. After reaching Babylon