The blurb for this movie which you can download online says:

"Stationed to work side-by-side on a mission in post war Germany, French army officer Henry Rochard (Grant) and American WAC Lieutenant Catherine Gates (Ann Sheridan) fall in love. But just when they decide to marry, Catherine is ordered back to the US - alone! The only way for an alien, including her husband, to enter the US with her, is through the congressional act governing war brides. So- the resourceful Catherine does the obvious —disguises her husband as a sister WAC in this hilarious classic..."