The functioning of the military is based on high morale, trust, and close professional and personal relationships. Achieving this requires commitment and self-sacrifice and to put the interests of the team ahead of one’s personal interests. Thus while operations and military life will frequently prove tiring, individuals should put the long term interests of the team ahead of themselves.
Tired people are more likely to make mistakes. It is up to the commander and the team to ensure that work is shared fairly. As well as looking after their personnel, good leaders understand that they also need to take opportunities to rest when possible to prevent fatigue affecting performance.
Values and Standards of the British Army, January 2008.
http://www.army.mod.uk/documents/general/v_s_of_the_british_army.pdf