The U.S. Army identifies eight core leadership competencies. One of these--leading by example--exemplifies the warrior ethos. The leader is always required to behave in a way that provides those under his or her command with a positive and effective role model.
The warrior ethos is a value that is eschewed by the U.S. Army.
The Army defines it as the adherence to a code that includes always putting the mission first, never accepting defeat, never quitting, and never leaving behind a comrade who has fallen.