The government of France signed an armistice with Germany and relocated the seat of government to the city of Vichy in 1940, leaving the northern part of France (including the capital city of Paris) to German forces. This French State is known in history as Vichy France and included territory in Morocco and Algeria. The movie Casablanca takes place during this time, the Nazi's serving as the ultimate symbol of evil and oppression.
The French North African territories were officially Nazi controlled but rumors of mixed loyalties were circulated and the Allied powers believed these people could be convinced to support the allied cause.
General Dwight D. Eisenhower planned an amphibious invasion of French North Africa, Operation Torch. Up to this point the Soviet Union had been adamant about the Allied Powers opening a second war front against the German Army and this was the initial engagement which saw the Germans being attacked from both sides.
Local French resistance was instrumental in the capture of Algiers.
The lessons learned during Operation Torch served Eisenhower well during his most famous amphibious landing, Operation Overlord– better known as D-Day, or the Invasion of Normandy.