Plans for the Allied counter offensive after the attack on Pearl Harbor were ongoing by mid @-@ 1942 . An invasion of Europe in 1943 would be unworkable , but the allies could attack the " soft underbelly of Europe " through the Mediterranean , as Prime Minister Winston Churchill put it . Devised by President Franklin Roosevelt and Churchill and code named Operation Torch , the plan was to occupy French North Africa : Morocco , Algeria , and Tunisia . From these French colonies , attacks could be launched that would drive Italy out of the war .