What are the duties of the Chief of Defence Staff (CDS) as Head of the Department of Military Affairs?
1. Permanent Chairman of Chiefs of Staff Committee
2. Exercise military command over the three Service Chiefs
3. Principal Military Advisor to Defence Minister on all tri-service matters
Select the correct answer using the code given below.

The correct option is 1 and 3 only.

To understand why this is the correct choice, let us analyze the duties and role of the Chief of Defence Staff (CDS) as the Head of the Department of Military Affairs (DMA):

1. Permanent Chairman of the Chiefs of Staff Committee (CoSC):
The CDS functions as the Permanent Chairman of the Chiefs of Staff Committee. In this role, the CDS helps in fostering inter-service cooperation, integration, and synergy among the Army, Navy, and Air Force. Therefore, statement 1 is correct.

2. Military Command over the Service Chiefs:
The CDS does not exercise military command over the three Service Chiefs. The three Service Chiefs (Army, Navy, and Air Force) continue to exercise administrative and operational command over their respective services. The CDS is a "first among equals" and acts as a coordinator rather than a military commander over them. Therefore, statement 2 is incorrect.

3. Principal Military Advisor to the Defence Minister:
The CDS acts as the Principal Military Advisor to the Minister of Defence (Raksha Mantri) on all tri-service matters. The individual Service Chiefs continue to advise the Defence Minister on matters relating exclusively to their respective services. Therefore, statement 3 is correct.

Since statements 1 and 3 are correct, and statement 2 is incorrect, the correct answer is indeed 1 and 3 only.