Why did India devalue its currency in 1966?

India devalued its currency on 6th June, 1966 as independent India faced its first balance of payment crisis. India was dependent on economic aid from rich countries, exports from India were very poor, there was not much encouragement for foreign investments, and India was facing a huge trade deficit. You can read about the Balance of Payment Crisis, 1991 – Causes and Measures to Control it in the given link.

Further readings:

1. Forex Reserves – Meaning, Importance, Advantages (Notes for UPSC IAS exam)
2. New Economic Policy of 1991 – Objectives, Liberalisation, Privatisation, Globalisation