The Mouse That Roared is a 1959 British satirical Eastman Color comedy film based on the 1955 novel The Mouse That Roared by Leonard Wibberley. It stars Peter Sellers in three roles: Duchess Gloriana XII; Count Rupert Mountjoy, the Prime Minister; and Tully Bascomb, the military leader. It also co-stars Jean Seberg. The film was directed by Jack Arnold, and the screenplay was written by Roger MacDougall and Stanley Mann.
The minuscule European duchy of Grand Fenwick is bankrupted when an American company comes up with a cheaper imitation of Fenwick's sole export, its fabled Pinot Grand Fenwick wine. Crafty prime minister Count Mountjoy (Peter Sellers) comes up with a plan: Grand Fenwick will declare war on the United States, then surrender, taking advantage of American largesse toward its defeated enemies to rebuild the nation's economy. Grand Duchess Gloriana (also Sellers) is hesitant, but agrees to the plan. Mild-mannered game warden Tully Bascome (also Sellers) is charged as Field Marshal to lead the Fenwick troops, aided by sergeant Will Buckley (William Hartnell).