Hi aspirant,
Here is the list of few colleges that provide with phd in defence and strategic studies-

Savitribai Phule Pune University : Department ofDefence and Strategic Studies, Pune.

Guru NanakCollege, Chennai.

Punjabi University : Department ofDefence and Strategic Studies, Patiala.

University of Madras : Department ofDefence and Strategic Studies, Chennai.

North Maharashtra University, Jalgaon.
Etc.

Requirements-
The candidate should have passed in Post-graduate degree of any other recognized university with the concerned subject or in an allied subject. The minimum required oercentage in post graduation varies from colleges to college but on average it lies around 55%
Hope this helps.