Operation Torch was an Allied invasion of Algeria and Morocco, two countries at that time under control of Vichy France, which resulted in opening of the second front against the Axis in North Africa.
An Allied invasion of Algeria and Morocco (Tunisia being excluded because was in the Luftwaffe's range) would have caught in a vise the German-Italian army under Rommel's command, which was fighting at El Alamein with the British Eighth Army of General Montgomery.
As the French forces from Algeria and Morocco were under the Vichy government's control, obedient to Germany, the Allies did not know how they will react. The French had colonial infantry, combat aircraft, warships and coastal batteries which could have given headaches to any invader.
The primary objectives of the Allies were the ports of
Casablanca (Morocco), Oran and Algiers (Algeria), which could then
serve to bring new troops and supplies. The air cover was to be provided
by U.S. escort aircraft carriers and the British base in
Gibraltar. An Anglo-American force was sent at Algiers, while American troops alone were sent at Casablanca and Oran.
On November 8, 1942, the Allied invasion began. However, as a French opposition was considered rather unlikely, the Allies did not conduct any preliminary aerial or naval bombardments. Although taken by surprise, the French nevertheless fought back.
The air force of Vichy France was active, which required the intervention of the Allied fighters. The French warships went out from harbors to attack the Allied fleet but were neutralized, and the coastal batteries opened the fire at Casablanca and Oran. The smallest opposition was at Algiers due to the neutralization of the coastal batteries by the French Resistance. Afterwards, the French opposed generally a low resistance on land.
The Allied Invasion of Algeria and Morocco also marked the first U.S. airborne operation in World War 2, the 509th Parachute Infantry Regiment capturing two airfields south of Oran.
After two days from the invasion's start, French Admiral François Darlan, commander of the Vichy government's forces, reached to an agreement with the Allies, and the French ceased to oppose. Therefore, Hitler ordered that the rest of France to be also occupied and new German-Italian troops were sent to Tunisia, trying to avoid a total defeat in North Africa.