I’m not convinced he actually is a jerk from the little conveyed by OP. He has everything to gain and nothing to lose by going long distance. If he wants to date other women while he is overseas and is really as awful a soldier-type as Anonymous suggests he is, then he would keep Lw’s niece on the hook as a backup plan and just go ahead and date other women without telling her. It sounds like he would feel too guilty doing that, although contact with her almost certainly would be a comfort. He may be trying to do the kind thing by setting her free. Now is a better time for that than after he meets another woman. She has most of the summer to recover from the breakup and thrive in the social and academic scene of her university. She will evolve at university. She shouldn’t spend her college years pining for some guy overseas, who has no idea where his military career will send him. He may know that he isn’t good at long-distance relationships. Most people aren’t.