Why cant I send messages to a friend who has moved country?

I was texting and calling a friend who was stationed in afghanistan. He moves around alot and was supposed to go to Germany next, but was stopping off in other countries. any messages i try to send fail to deliver and my calls are not diverted. Should the calls not automatically divert?? ive tried adding in the german country code, but this doesnt work. im afraid im missing a number or something. i would really appreciate if someone could help me, ive tried everything and am really worried................