The post-Vedic period of the Second Urbanisation saw a decline of Brahmanism. With the growth of cities, which threatened the income and patronage of the rural Brahmins; the rise of Buddhism; and the Indian campaign of Alexander the Great (327-325 BCE), the rise of the Mauryan Empire (322-185 BCE), and the Saka invasions and rule of northwestern India (2nd c. BC - 4th c. CE), Brahmanism faced a grave threat to its existence.