This is not an uncommon scenario. Deployments tend to do this to people. They become fearful that the time apart will hurt the relationship. They hear the stories of cheating and they want to distane themselves or rather, protect themselves from it, even though there is a very good chance it will never happen to them.
I would stay in touch with him. Let him know that you are still here, and still very much a part of his life, as a friend. That support will mean the world to him while he is gone, and if, upon his return, you decide to get back together, you will both know that your relationship can survive.
At least that is my humble opinion.
Thanks for your advice. That's pretty much what I had resolved to do. I asked him how best I could support him while he was away, and he said to be his friend.
He left for training today. I take solace in the fact that he'll still be in the US for a few more weeks, and I can still reach him by phone.