Why are some men heroes and other men cowards? Why do some men stay and fight and others flee from the battlefield? Secular authors and economics professors Dora Costa and Matthew Khan explored this question by looking at factors that affected deserters during the Civil War. Their conclusion: relationships. In their book Heroes and Cowards,the Social Face of War, they state:

Four brave men who do not know each other will dare not attack a lion. Four less brave, but knowing each other well, sure of their reliability and consequently of mutual aid, will attack resolutely.