Eisenhower, however, thought an invasion might not be necessary. In a letter to Lt. Gen. Carl Spaatz, the commander of Northwest African Air Forces, Ike explained that he wished to make the upcoming Operation Corkscrew “a sort of laboratory to determine the effect of concentrated heavy bombardment on a defended coastline.”
He wanted the Allied air forces to “concentrate on everything” so that the damage to the island, its military garrison, its equipment and morale would be “so serious as to make that landing a rather simple affair.” He remembered the effect on morale of the heavy shelling of the defenders of Corregidor the previous year and wanted “to see whether the air can do the same thing.”
Lieutenant General Spaatz’s Northwest African Air Forces had several subordinate units, two of which—the Northwest African Strategic Air Forces commanded by Maj. Gen. Jimmy Doolittle and the Northwest African Tactical Air Forces under Air Vice Marshall Arthur Coningham—would provide the aircraft for the bombing “laboratory” on Pantelleria.
These two commanders had at their disposal 1,017 aircraft of all types, the majority of which were fighters and bombers. The Corkscrew planners relied heavily on Doolittle’s strategic air forces for most of the hitting power. This force consisted of four groups of Boeing B-17s, two of North American B-25s, three of Martin B-26s, three of Lockheed P-38s, and one of Curtiss P-40s.
The British contribution to Doolittle’s command included several wings of Wellington medium bombers. While the pursuit group’s main task was providing escort to the bombers, they also participated in strafing and dive bomb attacks on the island.
The Corkscrew planners divided the air attacks on Pantelleria into two phases. From the end of May through June 6, 1943 (D-5), the island would be subjected to increasingly heavy bombardment. From June 7 (D-4) until dawn on June 11 (D-day), the island would be attacked around the clock with an intensity growing from 200 sorties on the first day to 2,000 sorties on the last day.
For the second phase, Doolittle’s forces would be joined by Air Vice Marshal Coningham’s tactical air force. This force was comprised mostly of North American A-36 dive bombers and P-40s. One of the tactical air force’s P-40 squadrons was the 99th Pursuit Squadron, the famed “Tuskegee Airmen,” which had just arrived in Tunisia the month before. The escort and attack missions against Pantelleria would be the first combat for the black airmen.
The deployment strategy chosen by Corkscrew planners would task the American aircraft to fly the day missions and leave the night bombing largely to the RAF with their Vickers Wellingtons. The Casablanca Conference had just recently concluded that the Allies would employ this tactic of round-the-clock bombing in their air campaign against Germany. Pantelleria would be their first attempt to bring day and night bombing to the enemy.
To augment the air bombardment, a Royal Navy strike force of four cruisers, eight destroyers, one gunboat, and 10 motor torpedo boats was organized to shell the island from time to time. These attacks would be aimed not so much as to inflict great damage but to test the island’s defenses and make the coastal artillery unmask its positions for targeting by the air forces.
These periodic shore bombardments were also directed against various targets on the island to keep the defenders guessing as to the direction of the impending assault. This strike force was augmented by other patrol boats to form a blockade of Pantelleria, preventing resupply by sea from Sicily. The blockade was integral to the plan of forcing the island to surrender prior to an invasion.
A U.S. Geological Survey report on the island stated it lacked any surface water. Its sources of fresh water were limited to a few springs in the volcanic rock, a small water desalination plant, and perhaps some underground cisterns for water storage. These sources were deemed adequate for the prewar civilian population of about 10,000, but with the augmentation of almost 12,000 military on the island the garrison and the civilian population faced water shortages.
Despite the presence of a blockading force around Pantelleria, the island was never totally isolated. Supplies continued to be brought to the island largely at night by small fishing boats and ferries throughout the air campaign. In addition, the occasional Junkers Ju-52 transport planes were able to bring supplies to the island and to evacuate almost all of the German troops.
Photoreconnaissance flights over the harbor of Pantelleria during the last week in May showed small craft had offloaded an estimated 530 tons of supplies overnight.
Air power had never before been applied to the problem of neutralizing strongly defended, well-manned fortifications from the air. Even under ideal conditions, the task was daunting. The planners of the upcoming “laboratory” on aerial bombardment were faced with a dilemma. With all the air power at their disposal, how could they best apply it to the garrison on Pantelleria to force surrender without the need of a seaborne invasion?
The answer came from an unlikely source: a South African-born primate research anatomist at the University of Oxford named Solly Zuckerman. He had volunteered his services to the British government at the outbreak of the war and had been involved in several research projects, one of which was the study of the effects of bombing on people and buildings.
The British Combined Operations Staff had offered to loan Zuckerman to the North African Air Force campaign planners to analyze the relation between effort and effect of the bombing of Pantelleria. This relation of effort and effect became the basis of the science of Operations Research—the application of analytical methods to predict results and make better decisions.
Zuckerman’s analysis of heavy bomber accuracy indicated that to destroy a gun position a 1,000-pound bomb would have to land within eight yards of the target. This would yield a circular area of destruction of 200 square yards. Secondary effects of the explosion, such as shock wave, shrapnel, and earth upheaval, would extend the vulnerable area to 600 square yards. To achieve this accuracy, as many as 400 1,000 pound bombs would have to be dropped.
With more than 100 identified gun positions on the island, it was clear that despite the armada of bombers at their disposal the Allied air forces could not knock out the defenses of Pantelleria in the time allowed.
Zuckerman reasoned that if as little as 30 percent of the guns could be rendered non-effective (i.e., two out of a six-gun battery) the remainder of the guns would be silenced for secondary reasons. These reasons included damage to fire control optics, casualties among the gun crews, disruption in communications, interdiction of ammunition resupply to the guns, and demoralization of the surviving crewmembers due to repeated exposure to the concussive effects of bombing.
A 30 percent reduction in the enemy’s defenses was deemed achievable by the resources at the planners’ disposal, and thus Zuckerman’s analytical methods became the cornerstone of the Corkscrew air campaign.
Immediately after the surrender of Axis forces in Tunisia on May 13, 1943, the focus of the Northwest African Strategic Air Forces was turned on Pantelleria. Bombing began in earnest on May 18 with U.S. fighter bombers and medium bombers by day and RAF Wellingtons by night. Early targets were the town and port facilities and the airfield.
In accordance with the targeting plan, the tonnage of bombs dropped increased almost daily, and new targets were chosen or old targets revisited based on daily reconnaissance flights over the island. By the end of May, 90 tons of bombs were being dropped daily.
On June 1, the Northwest African Strategic Air Forces heavy bombers, the B-17s, joined the attack. Early raids on the airfield by fighter-bombers strafing and medium bombers dropping 20-pound fragmentation bombs had destroyed most of the aircraft dispersed in the open surrounding the runway; however, no significant damage had been observed to the underground hangar complex.
On that day, a P-38 pilot skipped a 1,000-pound bomb into the blast door of the hangar but caused little damage. Several more attempts at skip-bombing the hangar’s entrance would be attempted in the coming weeks, but the structure and its contents remained undamaged throughout the campaign.
Early on, it became obvious to targeting planners that Professor Zuckerman’s seemingly pessimistic estimates of the number of bombs needed to destroy a target were being borne out by the facts. The bombs available to the Allied air forces were 1,000-pound, 500-pound, and 250-pound general-purpose bombs with either a 0.25-second delay fuse or instantaneous fusing options. These thin-walled bombs were designed to maximize their blast effects and had minimal penetrative capability against hardened targets.
Photo interpreters observed that instantaneous-fused bombs were having no effect on guns in revetments unless they scored direct hits, and the delayed-fused weapons would sometimes break apart on the volcanic rock prior to detonation.
The U.S. Army Air Forces (USAAF) would introduce new types of general-purpose bombs—the M64 500-pound and the M65 1,000-pound bombs—with thicker cases and better fusing options in 1943, but they would not arrive in theater until after the invasion of Sicily.