He's not sure when it happened, when they ceased being Hawkeye and BJ and transformed into something else entirely, a whole new entity; Hawk and Beej. He supposes it happened somewhere between the gin and blood, a quarter to death and half-past exhaustion.
He's not sure when it happened and he's not sure why. He's not even sure he likes it, not completely. But it came, it went, it stuck, and he's glad, as much as he hates what it means.
It's the absolute helpless acceptance of Korea, he supposes, that gets to him more than being Hawk and Beej.