What is the primary duty of a military personnel to his country?

It depends the situation. If it is in operation, I mean war time then his primary duty is to defend his country. If it is peace time then his primary duty is to make himself fit for the country by taking proper training. Whatever the situation always keep in minds three things---- Sincerity, Honesty and hard work.

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Protection of the territorial integrity & sovereignty of his country.

Remain loyal and disciplined. Must always adhere to lawful command. For this:

1. Remember there is always a commander, so always follow the lawful orders in true letter and spirit.
2. Do your best, dont worry about results.
3. Just concentrate on your task only, trust every one up, down and side ways.
4. Protection of geographic, ideological and psychological fronteers is soldier's responsibility.
5. Know SOPs, orders and instructions clearly.