Possible Clues:

• Not make so bold as to be fellow-guardians
• Each of them is "one who, in a perilous emergency, thinks with his legs": Bierce
• They shun conflict in barracks
• They're not bold enough to make fellow-places in hospitals
• '-- die many times before their deaths'
• Some runners
• Flight specialists?
• Fellow children being looked after -- they show fear
• Combat in Call of Duty's for wimps!
• ''Thus conscience doth make ... of us all'' (Hamlet)