There’s hazing in the military too. But rites if passage is different than what I’m talking about. Hazing in particular isn’t shared suffering, because it’s one person or group doing it to another while not going through it at the same time. I wonder if there may also be an aspect of suffering needing to be coupled with purpose.
Understood, and that's what I was pointing to with the slightly different idea of a rite of passage. But I think there's an important distinction that impacts the bonds that are formed. For example, all Marines went through the roughly equivalent rite of passage of boot camp. Given that, a Marine who served in Iraq may still feel some camaraderie when meeting a WW2 Marine, but probably not to the same level as another veteran from Iraq because the bond from the latter has closer, shared experience. And when it comes to someone who served in the same unit, the bond will likely be greater still. I think there's an aspect of psychological distance that is relevant to the bond.