After the Persians, the Greeks were the second invaders who invaded India in
the fourth century BC. Alexander ascended the throne of Macedonia after the
death of his father Philip in 334 BC. By 329 BC he conquered the whole of
Persia stretching from Asia Minor to Afghanistan. He crossed the Hindukush
in May 327 BC and spent the rest of the year in subduing the wild tribes.
Alexander sent Hephaestian and Perdiccas in advance with the bulk of his
army to invade India. They crossed Khyber pass in December 327 BC or
January 326 BC and built a bridge over the Indus. Meanwhile, Alexander was
busy in consolidating his position in the newly conquered territories.
    On the eve of Alexander’s invasion, several petty chiefs and independent
tribes were ruling the north and north-west India. They had been wasting
energy and resources in internecine quarrels and domestic feuds. Animosity
between the rulers of Taxila and Paurava provoked the former to send his son
Ambhi to Bactria to assure support to Alexander against the other rulers of
India. Alexander crossed the Indus with the help of a bridge of boats built at
Und or Ohind, about ten miles upstream of Attock. He was courteously
received by Ambhi, the ruler of Taxila who had succeeded his father in the
meantime. Here, Alexander sent a message to Porus to submit, who refused
and prepared for a showdown.
                            Alexander’s conquests