As we reflect on World War II, our minds are often drawn to the atrocities of genocide, and graphic depictions of Nazi Concentration camps throughout Europe. Others reflect on the near 30 million deaths, civilian and military, that occurred in the fierce, destructive battles on the Eastern Front. Few reflect on the "largest, longest, and most complex Naval battle in history," the Battle of the Atlantic. This study analyzed the Battle of the Atlantic from September of 1939 to May of 1945. While studies of the Battle of the Atlantic have traditionally focused on the German submarine offensive, this thesis evaluated the effectiveness of the Italian submarine force as a force multiplier to the German offensive during both coordinated and independent submarine operations (in the Atlantic) from October 1940 to July 1943. This study found that while the Italians provided capable submarines to the German High Command for use in the Atlantic, they were largely ineffective during coordinated operations from October 1940 to May 1941. The research concluded that ineffective coordinated operations resulted from inadequate joint training prior to the conduct of coordinated operations and a failure by the German High Command to treat Italy as a capable ally. Although ineffective during coordinated operations, the Italian submarine force did show improved performance during independent operations from June 1941 to July 1943.