stern commitment

[Waawe]

The Secretary of the Navy, James Forrestal, had decided the previous night that he wanted to go ashore and witness the final stage of the fight for the mountain. Now, under a stern commitment to take order from Howlin' Mad Smith, the secretary was churning ashore in the company of the blunt, earthy general.

Hello,

will someone help me understand the phrase "stern commitment" in the above sentence? Can you suggest a synonym or something ? Thanks a million.

[mykwyner]

It means that his commitment [promise] was serious and he would not compromise or relent.