This operation was considered so top secret that Hitler refused to issue a written order. Instead, he communicated verbally his desire that Field Marshal Erwin Rommel should assemble and ultimately command 11 divisions for the occupation of Italy to prevent an Allied foothold in the peninsula.
The Salerno landing (Operation Avalanche) was not the first by the Allies on the Italian mainland. On 3 September Montgomery’s Eighth Army had crossed the Straits of Messina to take Reggio Calabria as a preliminary to the occupation of the toe of Italy. Hitler had nevertheless decided to discount this move as unimportant, a view shared by Montgomery, who was disgruntled at being shunted into a secondary role. The Salerno landing, by contrast, stirred Hitler to order Operation Alarich to begin. Although he failed to prevent the sailing of the Italian fleet to Malta as required by the armistice terms, the Luftwaffe did succeed in sinking the battleship Roma en route by release of one of its new weapons, a guided glider bomb. In almost every other respect, Operation Alarich (now codenamed Achse) worked with smoothness.
Washington was reluctant to commit forces to Italy because it was determined the Alliance should launch an invasion of north-west Europe without avoidable delay. Accordingly, it was very much to Hitler’s advantage that Eisenhower’s lack of landing craft and divisions had obliged him to go ashore so far to the south. In consequence Hitler was able to use the divisions which had escaped from Sicily to concentrate against the Avalanche forces, while he deployed those brought from France and elsewhere (the 1st SS Panzer Division was temporarily transferred from Russia for the mission) to occupy Rome and subdue the Italian army in the centre and north of the peninsula. Before the invasion he had received contradictory advice: Rommel, one of his favourites, had warned against trying to hold the south; Kesselring, the general on the spot and an acute strategic analyst, had assured him that a line could safely be established below Rome. He now employed both men’s talents. While Rommel took charge of the divisions which had been rushed through the Alps to put down military and civilian resistance in Milan and Turin (and to recapture the tens of thousands of Allied prisoners liberated from captivity on Italy’s defection), Kesselring organised the Tenth Army in the south to check and contain the Salerno landing.
German troops elsewhere moved rapidly to disarm and imprison Italian troops or extinguish their resistance when it was offered. The areas of Yugoslavia under Italian occupation were brought under German control or that of their Croat (Ustashi) puppets. Italian-occupied France was taken over by German troops (with tragic consequences for the Jews who had found refuge there). Sardinia and Corsica, regarded as indefensible, were both skilfully evacuated, the former on 9 September, the latter by 1 October after a Free French invading force had come to the rescue of the local insurgents, who had risen in revolt on news of the armistice. In the Italian-occupied sectors of Greece the Germans actually scored a remarkable success against the run of strategic events. Encouraged by an outbreak of fighting between the Germans and the Italian garrison of the Ionian islands on 9 September (brutally put down by the Germans, who shot all the Italian officers they captured), the British, in the teeth of strong and wise American discouragement, invaded the Italian-occupied Dodecanese islands on 12 September and, with Italian acquiescence, took Kos, Samos and Leros. Sensing an easy success, offered by their local command of the air – as the Americans had perceived but the British refused to acknowledge – the Germans assembled a superior triphibious force, retook Kos on 4 October, forced the evacuation of Samos and seized back Leros by 16 November. The Dodecanese operation, painfully humiliating to the British, was then extended into the Cyclades. By the end of November the Germans directly controlled the whole of the Aegean, had taken over 40,000 Italian and several thousand British prisoners, and had actually set back the likelihood of Turkey’s entering the war on the Allied side – Churchill’s justification for mounting his second Greek adventure in the first place.
These were not the only chestnuts plucked by Hitler from the fire raised by Italy’s defection. On 16 September an airborne task force, led by an SS officer, Otto Skorzeny, rescued Mussolini from the mountain resort in the Gran Sasso where he was currently confined. Mussolini at once proclaimed the existence of an ‘Italian Social Republic’ in the north of the country; after 9 October it was to have its own army, formed from soldiers still loyal to him and led by Marshal Rudolfo Graziani, once governor of Libya and Wavell’s opponent in Egypt. The creation of Mussolini’s successor state to fascist Italy ensured that the growing resistance to German occupation of the north would swell into a civil war, with brutal and tragic consequences. To those consequences Hitler was entirely indifferent. Italy’s change of alliance relieved him of the obligation to supply a large part of the country with the coal on which it depended for energy; it added a captive labour force to the body of Italian volunteer workers in German industry; and it brought him nearly a million military prisoners who could also be set to work for the Reich.
Meanwhile the strategic effort to minimise the effect of the Allied invasion of the mainland was developing to his satisfaction. Rommel’s deprecation of the chances of defending Italy south of Rome had proved ill founded. Kesselring, by affiliation an officer of the Luftwaffe but by training and background a product of the general staff elite, had correctly argued that the Italian terrain lent itself admirably to defence. The peninsula’s central mountain spine, rising in places to nearly 10,000 feet, throws numerous spurs east and west towards the Adriatic and Mediterranean. Between the spurs, rivers flow rapidly in deep valleys to the sea. Rivers, spurs and mountain spine together offer a succession of defensible lines at close intervals, made all the more difficult to breach because the spine pushes the north-south highways into the coastal strip, where the bridges that carry them are dominated by natural strongpoints on the spurs above.
Salerno, the spot chosen by the Central Mediterranean Force staff for the main landing in Italy, falls exactly within this topographical pattern. Although the coastal strip is unusually wide and level (the factor recommending the beaches to the planners), it is dominated on all sides by high ground and the exit northward is blocked by the massif of Mount Vesuvius. Had Kesselring had sufficient force available at the outset, he might have formed the line across the peninsula that he had assured Hitler was militarily feasible, perhaps as far south as Naples. Commanding as he did, however, only seven divisions in his Tenth Army, of which the 16th Panzer alone was at full strength, he was obliged to commit what strength he had against the northern edge of the bridgehead with the aim of denying the invaders a swift exit towards Naples, and thus win time to construct a front above the city (eventually to be known as the Winter Position).
Despite the Tenth Army’s immediate weakness, it nevertheless gave the Avalanche force a bad time in the first week of the invasion. Mark Clark, the American general commanding the Fifth Army, had two corps under his command, the British X and US VI. Supported by overwhelming naval and air bombardments, both got easily ashore on 9 September. They were slow to exploit their initial superiority, however, and next day came under heavy counter-attack from German reserves, including those from the toe of Italy who had escaped Montgomery’s army. Counter-attacks by the 16th Panzer Division were particularly effective. On 12 September it retook from the British the key village of Battipaglia, close to their boundary with the Americans; the next day, together with 29th Panzergrenadier Division, it redoubled the pressure, threatening to break the bridgehead in half and cut the British off from the Americans who lost Altavilla and Persano and were preparing to re-embark their assault divisions. The Allies managed to stabilise the bridgehead by unleashing a tremendous weight of firepower on the advancing Germans. While the infantry of the US 45th Division took to their heels, the division’s artillerymen stuck to their guns and, with naval and air support, eventually halted the German Panzergrenadiers in their tracks.
By 15 September, thanks to the landing of British armour and American airborne infantry in the bridgehead, the crisis had passed. General Heinrich von Vietinghoff, in direct command of the Tenth Army, recognised that the balance of force had now shifted against him, and Kesselring accordingly sanctioned a fighting withdrawal towards the first of his chosen mountain lines further north. Montgomery’s Eighth Army had been reinforced by the British 1st Airborne Division, which on 9 September had landed at Taranto. On 16 September spearheads of the Eighth Army, advancing from Calabria, made contact with the Americans in the bridgehead south of Salerno. Two days later the Germans began their withdrawal, covering it by blowing the bridges in their rear as the Fifth Army pursued them. On 1 October British troops entered Naples. Meanwhile the Eighth Army had pushed two divisions, including the 1st Canadian, up the Adriatic coast to capture the complex of airfields at Foggia, from which it was intended to mount strategic bombing raids into southern Germany. In early October the Fifth and Eighth Armies established a continuous line across the peninsula, 120 miles long, running along the Volturno river north of Naples and the Biferno river which flows into the Adriatic at Termoli.