Delivering a lecture on "India in Peril" at the Aligarh Muslim University, Habib said the time had come for all nationalist forces to defend the principles on which this great nation was founded and which are enshrined in the letter and spirit of the country's constitution.
He said certain "forces have been unleashed" during the past year or so which were leaving no opportunity for "intimidating, polarising and weakening" the country.
It is ironical that the RSS which had refused to honour the national flag and Constitution right up till 1948 is today claiming the sole right to define nationalism and anti-nationalism, Habib said.
The RSS had been declared anti-national by free India's first government for not honouring the national flag and the Constitution and let off only after it apologised, the eminent historian said.