As Erwin Rommel's Afrika Korps regrouped in Tunisia in late 1942, the Allies began a blockade of the Germans with a relatively small number of planes and submarines. Rommel's campaign relied on sea and air supply lines across the Mediterranean and would be crippled if the flow of fuel and supplies was cut off. The American and British interdiction operation produced some of the fiercest air battles of World War II and one of only two successful submarine campaigns ever fought. It played a critical role in the Allied victory in North Africa.