[bumby]

One of the things that distinguishes the first three groups in your set is shared hardship. Many in the military (and elsewhere) think this is a necessary component to form those kinds of tight bonds. So it's not that they are "allowed" to have these feeling under life-threatening situations, it's that dire circumstances foster those feelings.

[SoftTalker]

Fraternity hazing is (was) supposed to create those bonds, but it's been drastically curtailed at most universities, and I'm not sure how well it ever worked (was never in a fraternity). In many cases it was just "here drink all this liquor and if it doesn't kill you, we'll initiate you"

[bumby]

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.

[hxugufjfjf]

Its shared, just not simultaneously. Its more a shared experience of «we all went through this suffering earlier»

[bumby]

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.