While staying closely aligned with Hitler, Mussolini remained carefully neutral until the summer of 1940. Then, with the wholly unexpected and sudden collapse of the French and British armies, Mussolini declared war on the Allies in the hope of making territorial gains in southern France and Africa. This decision proved a horrifying miscalculation, dooming Italy to its own prolonged and unwinnable war, immense casualties and an Allied invasion in 1943 which ushered in a terrible new era for the country.