The members of the United States Marine Corps (USMC) are famed for their intense devotion to one another  The Marine motto Semper Fidelis (Latin, Always Faithful) is taken to connote, among other things, the lifelong devotion a Marine has to his or her comrades in the corps
Psychologists who study cohesion among groups have concluded that the USMC creates this intense bond through its unique Recruit Training program
All branches of the armed forces have levels of internal cohesion much higher than typical civilian groups of similar aged individuals.