Unfortunately, of all the reasons for a US citizen to be out of the country, military service will undoubtedly be "the" one that definitely grants "natural born" status to children born off US soil. If there will be an exception to that, it would be for service people having children with non-US citizens (currently citizenship follows maternal lines.) I'd really love to exclude McCain on a technicality like this, but I can't in good conscience say I want to see children of service people who happened to be born outside the US excluded for all time just to get that.