Deep bonds are only strange to modern people.
“One only needs to look, for instance, at the failure of these intense bonds to hold primacy over the bonds of family, class or tribe when efforts are made to train ‘western’-style armies in non-western countries to see that the primacy of ‘comrades’ is socially contingent”
https://acoup.blog/2021/02/12/collections-the-universal-warrior-part-iib-a-soldiers-lot/