“My Son is in Iraq. His wife has left the state with his son, and has no intention of returning. Son wants divorce, and custody of child. I have his POA. Need help in how to proceed.”
She is at her right to file for a divorce. The Court will be unwilling to make permanent orders that will prejudice your son’s rights vis-a-vis the children on his return from active military service. However, it will make temporary orders to make sure that those children are taken care of. Your son will need local counsel in the divorce action, and an attorney experienced in issues faced by active military. He can probably get a referral through his branch of the military legal department.
Even with the POA, without your son’s active participation in the case, you may not be able to stop her from being temporarily able to move. That should be confirmed with your son’s local counsel.