Thursday, March 12, 2015

Interdiction WWII Part V - Northwest Africa November 1942-May 1943

The Germans and Italians launched a series of limited offensives in January and February to bloody Eisenhower’s forces before the formidable Eighth Army arrived from the east. In January, von Arnim’s Fifth Panzerarmee faced Anderson’s First Army in western Tunisia, while in the south the First Italian Army awaited the pursuing Montgomery. The heart of the First Italian Army’s position was the Mareth Line, a heavily fortified position, constructed by the French before the war against an Italian attack from Libya. It ran from the inland mountains through the town of Mareth to the sea, athwart the coastal plain that was the only route of advance for a large force. In late January, the Fifth Panzerarmee inflicted stinging setbacks on the British and French in a series of limited attacks near the towns of Ousseltia and Faid. The next month, von Arnim attacked the British through the Faid Pass toward Kasserine while Rommel, with the First Italian Army, struck at Gafsa through the Kasserine Pass. The inexperienced American I1 Corps retreated in disarray until it managed to make a stand at Thala. Rommel then withdrew back through the Kasserine Pass to resume his position on the Mareth Line. Von Arnim’s offensive also petered out, and by March 1 the Allies had recovered their original positions.

Even as they repulsed the Axis’ desperate thrusts, the Allies began to implement the strategy that in barely more than two months would result in their conquest of Tunisia. Not surprisingly, given the presence of both Coningham and Tedder, it was closely based on the three-stage model for a combined arms offensive developed in the Egyptian desert. The first task the Allies set for themselves was to wrest air superiority from the Axis. While still fighting for command of the air, the Anglo-Americans planned to turn their attention to the vulnerable convoys that plied the Strait of Sicily. An all-out offensive was planned for early May to destroy Heeresgruppe Afrika once it had been weakened logistically and denuded of air support.

Coningham set forth his plans for winning air superiority in an operations directive of February 10, 1943. He called for “a continued offensive against the enemy in the air” and “sustained attacks on enemy main airfields.” The attacks on the airdromes fell by day to strafing fighters and large formations of light and medium bombers, occasionally helped by heavy bombers from the Strategic Air Force. Light bombers, acting singly or in small formations, pressed the attack by night. The Germans noted with some surprise that in February and March the Allies began to place so much emphasis on counterair operations that they stinted on close air support for their ground forces.

German airfields in Sicily were inherently vulnerable: No radar protected them from surprise attack, and their coastal locations precluded antiaircraft defense in depth. Towns and olive groves, moreover, hemmed in the fields so that parked aircraft could not be dispersed properly. German airfields in Tunisia did permit adequate dispersion, and radar and observers protected them against surprise attacks. But incessant Allied air attacks forced the Germans to divide their aircraft among many small fields, which led to a considerable loss of efficiency.

The counterair campaign forced the Luftwaffe to devote a considerable portion of its strength to defending its bases: “Even the taking-off at the air bases,” a German study noted, “could often only be done with fighter protection. The forces set aside for safety measures had to be proportionally The Luftwaffe could ill afford this diversion of aircraft, for Allied air strength was growing rapidly while the Germans, short of industrial capacity and beset from other quarters, could barely replace their losses. While they had begun 1943 with more aircraft (690 combat aircraft) in and around Tunisia than the Allies (480 combat aircraft), their position deteriorated as the Anglo-Americans began to overcome their problems with basing and supply. The improvements permitted the Allies to fly into the combat zone not only aircraft that they had had to leave at Gibraltar or in Algeria but many new ones from Britain and the United States. By March 21 the two principal components of the Northwest African Air Forces-the Tactical and the Strategic Air Forces-disposed 1,501 combat aircraft, while German strength had risen not at all. At the end of the Tunisian Campaign (May 13), it was about what it had been in January-695 combat aircraft.

An interesting feature of the Tunisian Campaign is that the Allies were able to begin telling attacks on the Axis’ lines of communication before they had won general air superiority. Allied and German sources concur that the period of Allied air superiority over Tunisia began about April 1, while Allied aircraft had been regularly attacking the Axis’ convoys and ports since late February. This the Allies had been able to do because the Luftwaffe had to fight under a serious strategic disadvantage: Once the Allied air forces were established in Tunisia, the Axis’ lines of communication were wholly vulnerable, while those of the Allies remained largely exempt from retaliation. German aircraft based in Sicily and Sardinia tried to attack the Allied ports in Algeria and Morocco- Port Lyautey, Bdne, Oran, and Algiers-that sustained Eisenhower’s command, but their lack of range and ordnance-carrying capacity restricted them. No German fighters had the range to accompany the bombers, and when the Allies emplaced strong air defenses, the raiders’ losses quickly became insupportable. The same problems hobbled German efforts to attack Allied convoys. Even before the Allies had a numerical preponderance, the strategic asymmetry seriously disadvantaged the Luftwaffe, for the Allies, having comparatively safe supply lines, could mass their aircraft to win local air superiority. Lacking aircraft in numbers sufficient to contend for air superiority and to defend their convoys, the Germans had to concentrate upon protecting their vital supply lines. By conceding air superiority in this way, they facilitated the attacks on their air bases that progressively reduced their ability to provide air cover for the convoys.

On February 19, 1943, Eisenhower observed that the enemy was receiving about 75 percent of his requirements. “The termination of the Tunisian campaign,” he observed, “depends on the extent to which we can disrupt enemy lines of communications.” Tedder specified the priorities of the antishipping campaign in an operational directive of March 7, 1943, ordering that the “normal mission” of even the “strategic striking forces” was “the air attack of Axis sea, land and air lines of communications and supply to and from Tunisia.” Ships were the target of first priority. Tedder assigned the greatest importance to tankers traveling between Sicily and Tunisia. He ranked tankers sailing between Italy and Sicily next, and then freighters bearing military supplies. Ports followed ships in importance. The greatest priority went to Tunis and Bizerte, then came the other Axis-held ports in North Africa; the Sicilian ports of Palermo, Messina, and Trapani; and the Italian port of Naples.

The bombing of ports in Italy, Sicily, and North Africa fell to American heavy bombers-B-17s of the Twelfth Air Force and B-24s of the Libya-based Ninth Air Force. These attacks destroyed ships and supplies outright. Their chief effects, however, were to make an already marginal logistical system still less efficient and to expose the convoys to greater perils at sea. At Tunis and Bizerte the heavy bombers periodically destroyed or damaged the cranes used to unload the ships; they so demoralized the native laborers who manned the ports that eventually the importation of stevedores from Germany became necessary. A ship of 1,500 tons required a full day to unload, and a vessel of 5,000 tons required three days. This slowed down the turnaround time of convoys, thereby reducing the capacity of the system as a whole.

Kesselring’s optimism about supplying Tunisia had been based largely on the fact that the sea route from Italy to Tunisia was only about a third as long as that between Italy and Libya. Ships sailing to Tunisia would therefore be less exposed to air attack. They could also be protected from the Royal Navy by the very extensive minefields of the Strait of Sicily, the last of which was laid in the winter of 1942-1943. The original plan for supplying Tunisia had sought to take advantage of this protection by transporting supplies the length of Italy by rail and then ferrying them across the narrow and easily defended Strait of Messina to Sicily. At Palermo and other Sicilian ports supplies were to be transferred to ships for the short and protected run across the Strait of Sicily. But the advantages of this route were denied the Axis by the efforts of American bombers which, operating at short range, were much more effective against the Sicilian ports than they were against Naples. On March 22 American bombs ignited an explosion in the harbor of Palermo that devastated nearly thirty acres of docks and sank four merchant ships. In February, the bombers succeeded in forcing convoys to stage from Naples rather than from Sicily, tripling the distance they had to sail for Tunisia and thereby canceling the advantage of the Tunisian route over that of the Libyan. North of Sicily, moreover, convoys, unprotected by minefields, became liable to attack by British ships and submarines from Gibraltar.

Even the minefields of the Strait of Sicily ultimately redounded to the disadvantage of their creators. Their success in protecting shipping from surface attack was bought at the price of severe channelization of the convoy routes. The success of the British in laying minefields within those of the Axis worsened the channelization and resulted in a truly nightmarish problem of navigation for Italian seamen. Along the route of less than ninety miles from the western end of Sicily to Cape Bon the passage for convoys was nowhere more than three miles wide; for forty miles it was no more than one mile in width, and at some points less than half a mile wide. Within this narrow corridor the ability of vessels to manuever was constrained, and their vulnerability to aerial attack correspondingly increased.

The marginally adequate and severely channelized logistical system of the Axis gravely jeoparidized the supply of Heeresgruppe Afrika. But the final seal of doom for the enterprise was an Allied advantage that came to light only after the passage of more than three decades. The British, with some initial help from the Poles and the French, had succeeded in breaking many of the Germans’ most important ciphers. The information from this source, known as ULTRA, gave the Allies information about the Axis’ convoys that the official history of British intelligence in the Second World War describes as “virtually complete.” Daily digests disseminated to Allied air planners and naval commanders made known all points of origin, destinations, and schedules, and ships known to be carrying supplies of particular importance for Heeresgruppe Afrika could even be targeted specifically. The greatest secrecy shrouded the whole operation; targets, however tempting, were never attacked unless some other source duplicated the information, lest ULTRA be compromised.  Despite such precautions, the Germans at length realized the Al lies had very precise information about convoy movements, but drew the wrong conclusion about its source. Far from thinking their codes broken, they attributed the Allied information to disaffection in the ranks of their Italian allies.

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