It&#x27;s really to do with the incubation of a very strong shared culture and shared experience. For example the Royal Marines has a history going back 350 years, a shared language (google jack speak), and the longest and arguably hardest basic training in the world.<p>I believe it is possible, albeit in a slightly different form: elite sports teams and groups of people tied together with a strong shared purpose can get there I think.<p><i>edit</i> and yes, as marktangotango says - shared hardship and knowing you can count on the next guy because he&#x27;s been through what you have and hasn&#x27;t broken either is also key.