A number of officers of the Napoleonic era supposedly had mistresses along with them on campaign "disguised" as aides-de-camp (unbelievably, the "unfortunate" Mack was supposedly one). Pauline Fourès, Napoleon's mistress in Egypt, was smuggled on board ship in a chasseur's uniform by her husband.

https://www.napoleon.org/en/history-of-the-two-empires/articles/pauline-foures-napoleons-lover/