There are things you both don't know about each others lives now, yet underneath it all, both should still possess the qualities you first fell in love with... Just be there for him... greet him as you would have the day you got married if you still love him... Be honest though... both with him and with yourself. If you want this... want it to work... then make it work... if you don't, or are just not willing to make the sacrifices, at least let him be happy. If he still tried to call you during his deployment, it's because he is still thinking about you... and to me... if your asking this question, you're still thinking about him... even if you are still unsure of how you really feel.
When he arrives, don't focus on what you used to have, how he used to be, or what you think it should feel like. Let him know you are glad he is safe and tell him thank you... At the very least, he did serve his country... I know it sounds cheesy, but ask him out... First step to recovering a relationship would be to re-visit your friendship. You don't have to jump immediately back into the romantic parts... but if you do love him, take him out and see where things go... Just look at everything from a fresh new pair of eyes.
He is going to take some time to adjust back into the civilian life. He won't be carrying a weapon anymore, so occasionally you might catch him "looking" for something, but just give him a second and he'll realize it's not there. Even if he never left the wire during his stay overseas, he probably dealt with a lot of stress. Same as you have I'm sure trying to work on your bachelors... Share your experiences and listen to his. If you don't understand something he's talking about... make a mental note and try to google it later... that way he sees that you're taking initiative to learn what he's been doing. You are the one he fell in love with and visa versa... I could tell you all day about how to treat a deployed soldier... but only you know how you won him over the first time... Just re-visit those roots if you want to do it again...
Remember just to be honest with yourself and never give up on something you want as long as you're willing to get it...