The Department of Defence deals with the three Services i.e. Army, Air Force, Navy and Coast Guard. It also deals with Inter-Services Organization.
It is headed by Defence Secretary who is assisted by Director General (Acquisition), Additional Secretaries and Joint Secretaries. Defence Secretary is also responsible for coordinating the activities of the other Departments i.e. Department of Defence Production (DDP), Department of Ex Serviceman Welfare(DESW), and Defence Research and Development Organisation (DRDO) in Ministry of Defence.
