By opening up both the land and sea routes between India and Europ,it brought both of them to each other.
Indirectly this invasion made possible the establishment of Indo- Bacterian and Indo- Parthian states . which at a later stage considerably influenced Indian architecture (Gandhara school of sculpture ), astronomy, coinage etc.
The invasion opened the eyes of Indian politicians to the necessity of creating a unified empire.
The date of the Invasion of Alexander is the ‘first reliable date in early Indian history ‘ and considerably helps us in solving chronological difficulties.