few cases where the concept of moral duty makes the moral course of action clear?

Answer 1

Moral duty is the moral course of action. Duty, however does not have to be moral.

Example: General of the Army, personal moral code condemns homosexuality, but his duty as an officer in the Army requires that he cannot act upon his personal moral code unless the soldier admits voluntarily to homosexuality.

Answer 2

One example would be caring for our parents when they grow old is a moral duty of ours so the action to be taken is clear and no matter what the results are.

This is the basis of Kants idea of ethics

Answer 3

Never leacing a wounded soldier behind.