The process Allied invasion of Italy, was the Allied landing on mainland Italy in September 1943, by General Harold Alexander's 15th Army Group (comprising Mark Clark's U.S. Fifth Army and Bernard Montgomery's British Eighth Army) during World War II. The operation followed the successful invasion of Sicily during the Italian Campaign. The main invasion force landed around Salerno on the western coast in Operation Avalanche, while two supporting operations took place in Calabria (Operation Baytown) and Taranto (Operation Slapstick).
However, General George Marshall and much of the American staff wanted to undertake no operations that might delay the Normandy invasion. When it became clear that Operation Overlord could not be undertaken in 1943, it was agreed forces in North Africa should be used to invade Sicily, with no commitment made to any follow-up operations.
Joint Allied Forces Headquarters AFHQ were operationally responsible for all Allied land forces in the Mediterranean theatre, and it was they who planned and commanded the invasion of Sicily and the Italian mainland.
The Allied invasion of Sicily in July 1943, codenamed Operation Husky, was highly successful, although many of the Axis forces there were allowed to avoid capture and escape to the mainland. More importantly a coup deposed Benito Mussolini as head of the Italian government, which then began approaching the Allies to make peace. It was believed a quick invasion of Italy might hasten an Italian surrender and produce quick military victories over the German troops that could be trapped fighting in a hostile country. However, Italian (and more so German) resistance proved relatively strong, and fighting in Italy continued even after the fall of Berlin. In addition, the invasion left the Allies in a position of supplying food and supplies to conquered territory, a burden which would otherwise have fallen on Germany. As well, Italy occupied by a hostile German army would have created additional problems for the German Commander-in-Chief Albert Kesselring.
Prior to Sicily, Allied plans envisioned crossing the Strait of Messina, a limited invasion in the "instep" area (Taranto), and advancing up the toe of Italy, anticipating a defense by both German and Italian forces. The overthrow of Mussolini and the Fascisti made a more ambitious plan feasible, and the Allies decided to supplement the crossing of the Eighth Army with a seizure of the port of Naples. They had a choice of two landing areas: one at the Volturno River basin and the other at Salerno, both at the range limits of Allied fighter planes based in Sicily. Salerno was chosen because it was closer to air bases, experienced better surf conditions for landing, allowed transport ships to anchor closer to the beaches, had narrower beaches for the rapid construction of exit roads, and had an excellent pre-existing road network behind the beaches.
Operation Baytown was the preliminary step in the plan in which the British Eighth Army under General Bernard Montgomery would depart from the port of Messina on Sicily, to cross the Straits of Messina and land near the tip of Calabria (the "toe" of Italy), on 3 September 1943. The short distance from Sicily meant landing craft could launch from there directly rather than be carried by ship. The British 5th Infantry Division would land on the north side of the "toe" while the 1st Canadian Infantry Division would land at Cape Spartivento on the south side. British General Bernard Montgomery was strongly opposed to Operation Baytown because he predicted it would be a waste of effort since it assumed the Germans would give battle in Calabria; if they failed to do so, the diversion would not work, and the only effect of the operation would be to place the Eighth Army 300 miles (550 km) south of the main landing at Salerno. He was proved correct; after Operation Baytown the Eighth Army marched 300 miles north to the Salerno area against no opposition other than engineer obstacles.
Plans for the use of airborne forces took several forms, all of which were cancelled. The initial plan to land airborne forces near Salerno in Military gliders as part of Operation Avalanche gave way to Operation Grant, in which they would seize and hold crossings over the Volturno River. This was deemed logistically unsupportable and replaced tentatively by Operation Grant II, a drop of the 82nd Airborne Division on airfields near Rome. Because of the distance from the Allied beachheads at Salerno, this required the active cooperation of Italian forces, and 82nd Airborne Assistant Division Commander Brig. Gen. Maxwell D. Taylor was spirited into Rome to negotiate. Taylor's judgment was that the operation would be a trap and he advised cancellation, which occurred September 8.
The main landings (Operation Avalanche) were scheduled to take place one week later on 9 September, during which the main force would land around Salerno on the western coast. It would consist of the Fifth United States Army under Lieutenant-General Mark W. Clark, comprising the U.S. VI Corps under Major-General Ernest J. Dawley, the British X Corps under Lieutenant-General Richard McCreery, with the U.S. 82nd Airborne Division in reserve, a total of eight divisions and two brigade-sized units. Its primary objectives were to seize the port of Naples to ensure resupply, and to cut across to the east coast, trapping Axis troops further south. The British 1st Airborne Division would be landed by sea near Taranto, on the "heel" of Italy in Operation Slapstick, as a diversion for Salerno. Their task was to capture the port and several nearby airfields and link with the Eighth Army before pressing north to join the Fifth Army near Foggia.
The plan was daring but flawed; The 5th Army would be landing on a very broad 35-mile front, using only three assault divisions, and the two Corps were widely-separated both in distance and by a river. Furthermore, the terrain was highly favorable to the defender. A US Army Ranger force under Colonel William O. Darby consisting of three US Ranger battalions and two British Commando units was tasked with holding the mountain passes leading to Naples, but no plan existed for linking the Ranger force up with X Corps' follow-up units. Finally, although tactical surprise was unlikely, Clark ordered no naval preparatory bombardment or Naval gunfire support take place, despite experience in the Pacific Theatre demonstrating that it was necessary.
Six Nazi German divisions were positioned to cover possible landing sites on the western coast of Italy from Rome to the toe, including the Hermann Goering Panzer Division, 26th and 16th Panzer Divisions, the 15th and 29th Panzergrenadier Divisions, and the 2nd Fallschirmjäger (Parachute) Division. Heinrich von Vietinghoff, the German Tenth Army commander, specifically positioned the 16th Panzer Division in the hills above the Salerno plain.
In Operation Baytown on 3 September 1943, the first troops ashore on the mainland were the British Eighth Army, which included British and Canadian troops, under General Bernard Montgomery. Opposition to the landings was light; the Italian units surrendered almost immediately, leaving a single German regiment to defend 17 miles (27 km) of coast. Albert Kesselring and his staff did not believe the Calabria landings were the main Allied attack, the Salerno region or possibly even north of Rome being the more logical points of attack. He therefore ordered General Traugott Herr's LXXVI Panzer Corps to pull back from engagement with 8th Army and delay them with demolition of bridges. Thus Montgomery's objections to the operation were proved correct: the Eighth Army could not tie down German units that refused battle, and the main obstacle to their advance was the terrain and German demolitions of roads and bridges. By 8 September, Kesselring had concentrated Heinrich von Vietinghoff's 10th Army, ready to make a rapid response to any Allied landing.
On 8 September, before the main invasion, the surrender of Italy to the Allies was announced. Italian units ceased combat, and the Navy sailed to Allied ports to surrender. However the German forces in Italy were prepared for such an eventuality and moved to disarm Italian units and occupy important defensive positions.
Operation Slapstick commenced on 9 September, during which the British 1st Airborne Division was landed at Taranto, an important naval base. Since the Italians surrendered the previous day and since few German forces were in the area, the British troops were landed directly into the port from warships rather than carrying out an amphibious assault. Resistance was slight, and the town and ports were captured almost immediately and quickly secured with few losses.
X Corps, composed of the British 46th and 56th Divisions and a light infantry force of U.S. Rangers and British Commandos of Brigadier 'Lucky' Laycock's 2 Special Service Brigade, experienced mixed reactions to its landings. The Rangers were unopposed and seized their mountain pass objectives. The Commandos, from No. 2 Army Commando, came ashore against light resistance and captured the city of Salerno quickly. The two infantry divisions, however, met determined resistance and had to fight their way ashore with the help of naval bombardments. The depth and intensity of German resistance forced British commanders to concentrate their forces, rather than driving for a linkup with the Americans to the south.
At Paestum, the Germans had established artillery and machine-gun posts and dispersed tanks through the landing zones that made progress difficult. The 36th (Texas)Division had not been in combat before, and despite being slow to organize, the beach areas were successfully taken. Around 07:00 a concerted counterattack was made by the 16th Panzer Division (Major General Rudolf Sieckenius). It caused heavy casualties but was beaten off with naval gunfire support. To the south, the 1st Battalion of the division's 141st Infantry Regiment, was pinned down in an all day battle and out of radio contact.
Because the British and American beachheads were still separated by a five mile gap, all of which was in the area assigned to the two British divisions, the Corps boundaries were re-drawn to facilitate X Corps' operations, assigning most of the unsecured area to VI Corps. The two forces linked up by the end of day two and occupied 35-45 miles (55-70 km) of coast line to a depth of six or seven miles (10-12 km).
On the left of the VI Corps, where the U.S. 45th Infantry Division had landed and moved into the line to fill the area formerly assigned to 10 Corps, German Panzer units made significant gains. On 13 September, the right of the 45th Division gave way, driving a salient between the two American divisions where the Sele River and Calore Lucano river merged. The German armored attack, approximately 4 miles from the forward supply dumps on the beachhead, was stopped by artillery, naval gunfire, and a makeshift infantry position manned by artillerymen.
The forward units of both divisions were withdrawn behind the T. La Caso (river) to reduce the length of defensive lines. The new perimeter was held with the assistance of the 82nd Airborne Division. Two battalions (1,800 paratroops) of the 504th Parachute Infantry Regiment jumped on the night of 13 September inside the beachhead and moved immediately into the line on the right of VI Corps. The next night, with the crisis passed, the 505th Parachute Infantry Regiment also parachuted into the beachhead and reinforced the 504th. The 325th Glider Infantry Regiment, reinforced by the 3rd Battalion 504th PIR, landed by sea on 15 September.
With strong naval gunfire support, and well-served by Fifth Army's artillery, the reinforced and reorganized infantry units defeated all German attempts on 14 September to find a weak spot in the lines. German losses, particularly in tanks, were severe. German probes continued on 15 September, but when it became clear early on 16 September that the Allies were too strong and well-positioned to be displaced, von Vietinghoff ordered 10th Army to withdraw to the north, covered by skilled delaying actions. Patrols in both Allied corps areas on 17 September found that the Germans had broken contact everywhere on the beachhead, and after re-securing all objectives on 18 September, Fifth Army began its advance north.
General Mark W. Clark was awarded the Distinguished Service Cross, the second-highest U.S. award for valor in combat, for his front-line leadership during this crisis. He was frequently seen in the most forward positions encouraging the troops. However, in the opinion of historian Carlo D'Este, Clark's poor planning of the operation caused the crisis in the first place. Clark himself blamed the slowness of the Eighth Army for the beachhead crisis, for which there was at least some validity. On 9 September, the day of the landings, Montgomery had stopped his advance for two days to give Eighth Army a rest.
The Salerno battle was also the site of the Salerno Mutiny instigated by about 600 men of the British X Corps, who on 16 September refused assignment to new units as replacements. They had previously understood that they would be returning to their own units from which they had been separated during the fighting in the North African Campaign, mainly because they had been wounded. Eventually the corps commander, McCreery, persuaded most of the men to follow their orders. The NCOs who led the mutiny were sentenced to death but were eventually allowed to rejoin units and the sentence was not carried out.
With the Salerno beachhead secure, the Fifth Army began its attack northwest towards Naples on 19 September. The 82nd Airborne, after suffering serious casualties near Altavilla Silentina, was shifted to X Corps, joining the Rangers and the British 23rd Armoured Brigade on the Sorrento Peninsula to flank the German defenses at Nocera, which the 46th (North Midland) Division attacked. The 7th Armoured Division, passing through the 46th Division, was assigned the task of taking Naples, while the newly landed U.S. 3rd Infantry Division took Acerno on 22 September and Avellino on 28 September.
The 8th Army had been making good progress from the "toe" in the face of German engineer actions and linked with the 1st Airborne Division on the Adriatic coast. It united the left of its front with the Fifth Army's right on 16 September and advancing up the Adriatic coast captured the airfields near Foggia on 27 September. Foggia was a major Allied objective because the large airfield complex there would give the Allied air forces the ability to strike new targets in France, Germany and the Balkans.
Squadron A of the King's Dragoon Guards entered Naples on 1 October (whose occupying forces had just been ejected by a popular uprising) and the entire Fifth Army, now consisting of three British and five U.S. divisions, reached the line of the Volturno River on 6 October. This provided a natural defensive barrier, securing Naples, the Campainian Plain and the vital airfields on it from German counterattack. Meanwhile, on the Adriatic coast, the British 8th Army had advanced to a line from Campobasso to Larino and Termoli on the Biferno river.
The subsequent success of the 10th Army in inflicting heavy casualties, and Kesselring's strategic arguments, led Hitler to agree that the Allies should be kept away from German borders and prevented from gaining the oil resources of the Balkans. On 6 November Hitler withdrew Rommel to oversee the build-up of defenses in northern France and gave Kesselring command of the whole of Italy with a remit to keep Rome in German hands for as long as possible.
By early October, the whole of southern Italy was in Allied hands, and the Allied armies stood facing the Volturno Line, the first of a series of prepared defensive lines running across Italy from which the Germans chose to fight delaying actions, giving ground slowly and buying time to complete their preparation of the Winter Line, their strongest defensive line south of Rome. The next stage of the Italian Campaign became for the Allied armies a grinding and attritional slog against skillful, determined and well prepared defenses in terrain and weather conditions which favoured defense and hampered the Allied advantages in mechanised equipment and air superiority. It took until mid-January 1944 to fight through the Volturno, Barbara and Bernhardt lines to reach the Gustav Line, the backbone of the Winter Line defenses, setting the scene for the four battles of Monte Cassino which took place between January and May 1944.