The cultural and historic antipathy there is already huge. So, two nations with a long border and a history of mutual hatred both have too many unattached young men...

Too many rootless young men? Put them in the military and send them to kill the other big group of rootless young men.

There was already talk about the long-term results of female infanticide when it began to come to light, I remember, many years ago. An upturn in violence was one projected outcome even then. The nations with the problem have two choices: control it or let it control them. Putting all those men in the military and then throwing them at something is one alternative. I wonder if it will happen...