I can get a room, order food, and find my way about in Europe and Japan, but neither myself, nor my associates are fluent enough to hold our private conversations in their languages, nor do we feel the necessity. Please travel to any of the military bases in asia, and see for yourself, just how many contractors or military personnel can speak or hold their conversations in Japanese. If you travel that much, then you must know that very few people speak anything but their native language, when conversing amongst themselves.
I have never been in the military, but I travel enough, and my experience among private business has been the opposite, at least so once in the foreign country. On Air France we would speak French; on American carriers, English.