Alexander’s invasion had a two-fold political effect: By crushing the Achaemenian Empire it loosened the already feeble control of the Persians over Pakistan; and by creating a power vacuum in this area it encouraged, for the first time in history, intrusion by India into Pakistan. Fortunately for India, at this opportune moment a man from Punjab, Chandragupta Maurya, was able to set up a strong government in the Gangetic Valley which extended its sway over most of northern India. Alexander’s successor Seleucus who had yet to grid his loins and muster his forces after the Dictator’s sudden and unexpected demise, was prevailed upon by diplomacy to cede Pakistan to Chandragupta peacefully, avoiding the sufferings of war whose outcome seemed uncertain to him. Pakistan, as such, became a part of India’s Maurya Empire in 300 BC without war. This was the first time in history that Pakistan was looking eastward and the first time it had become part of India and ruled by India.
The Mauryan dynasty lasted about 180 years, nearly as long as Achaemenid rule, and began with Chandragupta Maurya, not to be confused with Chandragupta I of the much-later Gupta Dynasty. Chandragupta Maurya lived in Taxila and met Alexander and had many opportunities to observe the Macedonian army there. He raised his own military using Macedonian tactics to overthrow the Nanda Dynasty in Magadha. Following Alexander’s death on June 10, 323 BCE, his Diadochi (generals) founded their own kingdoms in Asia Minor and Central Asia. General Seleucus set up the Seleucid Kingdom, which included the Pakistan region. Chandragupta Maurya, taking advantage of the fragmentation of power that followed Alexander’s death, invaded and captured the Punjab and Gandhara (NWFP). Later, the Eastern part of the Seleucid Kingdom broke away to form the Greco-Bactrian Kingdom (third century–second century BCE).
Chandragupta’s grandson Asoka (273-232 BCE), is said to have been the greatest of the Mauryan emperors. Ashoka the Great was the ruler of the Mauryan empire from 273 BCE to 232 BCE. A convert to Buddhism, Ashoka reigned over most of South Asia and parts of Central Asia, from present-day Afghanistan to Bengal and as far south as Mysore. He converted to the Buddhist faith following remorse for his bloody conquest of the kingdom of Kalinga in Orissa. He became a great proselytiser of Buddhism and sent Buddhist emissaries to many lands. He set in stone the Edicts of Asoka. In Pakistan, nearly all of the Asokan edicts are written either in the Aramaic script (Aramiac had been the lingua franca of the Achaemenid Empire) or in Kharosthi, a script derived from Aramaic.
Brhadrata, the last ruler of the Mauryan dynasty, ruled territories that had shrunk considerably from the time of emperor Ashoka, but he was still upholding the Buddhist faith. He was assassinated in 185 BCE by his general Pusyamitra Sunga, who made himself the ruler and established the Sunga dynasty. The assassination of Brhadrata and the rise of the Sunga empire led to a wave of decline of Buddhists.