A common critic we hear about an EU wide army is What language are they gonna speak but let’s forget Europe 2024,
Rome had a huge empire over the whole Europe, I may be wrong, but I don’t think that commoner spoke proper Latin in remote province. What happens when they join the legion ? Would the units be split by origin region (Dacian with Dacian, Lugdunumese with Lugdunemese) with only officer speaking latin ? Or would you merge legionaries from different province (So you have Tingitanian, a Lustitanian and a Thracian in the same unit) and give them a crash course in military latin (the way the french foreign legion does? ) Even going as far as Rome, Karl the great empire also spread over half of Europe, and modern European nation used to be way more multi-lingual than they are today, and most likely a random southerner/northerner in Britain, France or Germany couldn’t talk to each other.
So how did ancient armies managed the language question ?
Armies don’t need complex phrases like “Last week did I see you go to the library?” And as such they’ve often used non-verbal communications in battle (especially because battle is fucking confusing) this has included drum signals, colored smoke, flags for different actions, and gestures.
When they are using verbal commands they’re often a greatly simplified set of phrases - sometimes in a jargon that isn’t even proper speech. It’s rare to see ten syllable commands and you’re much more likely to hear “company, right” than “Company of soldiers whom I command, please initiate a pinwheel rotation to the right around the rightmost file of your formation. Thank you kindly.” So if Europe had to form an army inter lingually then “a derech” and “a isker” would probably end up being right and left respectively… that or they’d follow the EU trend of “When in doubt, default to French”… or they’d just signal their troops with different patterns of Eurohouse beats.