A bit off topic but how about the airforce? English is the universal language for civilian aviation, so I'd imagine both sides to be reasonably proficient at it. Although judging from comments from other members, it is probably unnecessary due to the presence of translaters.They bring translators. As global as English is most people aren't really good at it. Most people never master a foreign language unless they live in a country that speaks a foreign language or get a degree in it. A lot of immigrants sound childish and rude even after years because they don't know nuances and idioms to the level of a native adult. There is no way two militaries would communicate in a language that is foreign to both sides.