What was the significance of Aryan and other tribal migrations on the Indus valley

The significance of Aryan and other tribal migrations on the Indus Valley. Harappa and Mohenjo Daro were both very busy cities that had citadels for protection from enemies and floods which were made of bricks fired in a kiln. This is unlike Mesopotamia ... The Aryans were led by chiefs called rajahs.

the significance of Aryan and other tribal migrations on the Indus valley was that this indeuopreanian people brougth new customs and religious approach to India and Indian civilization as we know it started to shape