Can anyone please show me some common military sayings used in the 1800s (or 1900s)? I found some sentences but they are all new... My story takes place before the invention of airplanes, missiles, etc.
I suggest that you find 19th century military books in the language(s) of your characters.
They can include books of tactics, books of military regulations, historical accounts by soldiers, and autobiographies.
You might also want to look up actual military records in the national archives of the country in question. You might be able to find reports, letters, official journals, etc.
And you might want to look up dicitnaries of slang and common phrases from that period, slang and phrases that people might get used to before jining the military, and dictionaries of military jargon.