"The Mouse That Roared" is a satirical novel by Leonard Wibberley, published in 1955. The story follows the tiny European nation of Grand Fenwick, which declares war on the United States in a desperate attempt to gain foreign aid. The plan backfires when they accidentally win the war, leading to unexpected consequences. The novel explores themes of power, politics, and the absurdity of war. It highlights how a small nation can inadvertently change the course of history through a series of comedic events. The book was later adapted into a film in 1959, starring Peter Sellers.