Advance to the Rear

Advance to the Rear is a lighthearted 1964 American western comedy film set in the American Civil War. It stars Glenn Ford, Stella Stevens and Melvyn Douglas and is directed by George Marshall. The film is based on the 1957 novel Company of Cowards by Jack Schaefer, with the film having that title in preproduction and when released in the United Kingdom. However, the novel had none of the comedic elements of the film which retained only the basic idea of a unit formed out of men who had been courtmartialed for cowardice and sent out west as well as some character names.

Captain Jared Heath, however, disturbs the status quo one day by going out and capturing some of the enemy. The Confederates feel obliged to retaliate. One thing leads to another and a military fiasco results. As punishment, Brackenbury and Heath are demoted, placed in charge of all the misfits General Willoughby can find and shipped west, where they can hopefully do no further damage.The rebels are suspicious, so they send a beautiful spy, Martha Lou Williams, to find out their real mission. After questioning Easy Jenny, a madam Martha Lou is traveling with, Heath sees through Martha Lous ruse. But he decides that he is going to marry her eventually, so Heath does his best to keep her out of mischief. ........

Source: Wikipedia