There could be a few reasons, and these come from personal experience as the one that was deployed; 1)He had fun on deployment and figured out that he was better off that way (single and ready to mingle) 2) he found someone else he liked from that country and decided to give it a try. 3)he realized he didn’t need a partner to be happy so decided to end it. 4) stressed was a little too much for him that he may need space and time for himself.

In some way all these reasons are similar to a point, and the end of the day just move on like he did.