The Olterra redesigned for Human Torpedo attacks
In early July 1941, Giuseppe Pierleoni arrived at the French consulate in Barcelona, Spain, to take up his new duties as a diplomat. Actually, that assignment was a cover. He was a commander in the Italian Navy, and he had been sent to Spain to organize and direct sabotage activities against the British bastion of Gibraltar.
Popularly known as the Rock, the British crown colony is perched on a peninsula just off the southern coast of Spain in the narrow entrance to the Mediterranean Sea. A limestone mass rising 1,408 feet above the water, the fortress is connected to the Spanish mainland by a low, sandy isthmus a mile and a half long.
Gibraltar was also a naval base, protected against submarine attacks by heavy steel nets. At any given time, there might be scores of Royal Navy vessels, from battleships to small boats, nestled in the relative safety of the harbor.
Commander Pierleoni, dressed in civilian clothes, spent most of the winter of 1941–1942 building up his sabotage organization in Spain. Then he was ready to launch his first land-based secret mission against British ships at Gibraltar. It would be an attack by twelve members of a combat swimming group known as the Gamma.
According to plan, the swimmers sneaked into a villa in Spanish territory just north of the Rock. They donned thick woolen undergarments, neck-to-toe rubber suits, camouflage-net helmets, and breathing equipment. Just before midnight on July 13, the Italian raiders left the villa and headed for the beach. Strapped to the back and chest of each man were five-pound explosive devices known as “bed-ring bombs.” Although small, the bombs could blow holes in steel plates.
Led by Vago Giari, tough and broad-shouldered with the proven dexterity of a seal, the swimmers knew they were on a perilous mission. The Rock was bristling with weapons, and large numbers of sentries were always on high alert—watching for saboteurs.
Nearing the Rock undetected, Giari and the others could see the dark silhouette of perhaps thirty Allied ships in the harbor. Each man was told his own target. Then the swimmers edged noiselessly into the water.
Back on the beach an hour later, Giari and five other frogmen heard four booms in the harbor. They knew the explosions would not sink the ships, but would put them out of action for a few months.
The operation was only moderately successful. Bombs were placed on ships only to have the explosives swept away by the current. Six swimmers did not return.
Giari was disappointed over the results of the raid and vowed to return. Two months later, he and another frogman sneaked into Gibraltar Harbor and badly damaged two British ships.
Now Commander Pierleoni turned his focus toward human torpedoes, using one of the war’s strangest bases for his operations. It was the Italian tanker Olterra, which had been scuttled in shallow water by her captain just inside the Spanish harbor at Algeciras, within sight of Gibraltar. He had taken that action to keep the ship out of British hands after Italy declared war against England in 1940.
Italian Navy Lieutenant Licio Visintini brought to the submerged ship a human-torpedo crew that had crossed Spain in civilian clothes and with fake passports. Although Spain was officially neutral, it cooperated wherever possible with Nazi Germany. So a few Spanish soldiers who had been assigned to keep an eye on the Olterra were far more interested in scrounging cigarettes and consuming brandy.
Visintini’s plan was to convert the half-sunken vessel into a base to launch underwater attacks against ships in Gibraltar Harbor. Keeping his mission as secret as possible, he told the Spanish soldiers that he was a civilian engineer who had been sent to try to salvage parts of the Olterra. The guards shrugged.
Working mainly at night to conceal their activity against any hostile eyes, the Italians used pumps to empty tons of water from the bow compartment until it rose out of the water. Then they cut out a door in the side of the compartment. Torpedoes would be kept in the bow, and when a night attack on Gibraltar Harbor was ready, they could be passed out of the ship through the door and lowered with pulleys to the water.
When renovation of the “base” was completed, Lieutenant Visintini explained to the Spanish soldiers that he was bringing boiler tubes from Italy by land. They again showed total disinterest. Actually, each crate contained a twenty-two-foot torpedo.
On December 7, 1942, all was ready for the first human-torpedo attack from the Olterra base against the closely guarded harbor. To discourage frogmen or human torpedoes, the Royal Navy dropped explosive charges into the harbor at irregular intervals. A steel net which could be lowered when an Allied ship approached, ringed the harbor.
Hidden by the veil of night, two torpedoes were lowered from the bow of the Olterra into the water. The Italians called a torpedo a maiale (pig).
Powered by an almost silent engine, a pig could travel at about three miles per hour and had a range of ten miles. It could travel on the surface or dive to a maximum of ninety feet. There was a warhead in the front section that could be detached by releasing an airscrew. Then the explosive could be attached to the hull of a ship.
Now Lieutenant Visintini got onto a seat at the front of one torpedo, and his partner took the rear seat. The back of one seat held steel cutters (to carve a hole in the harbor’s net) and magnetic clamps to fix a warhead to a ship’s hull. The man astride the pig in the forward position had controls for speed, steering, and diving, along with a luminous depth gauge for use below the surface.
Visintini and his companion cast off and reached the outer harbor in about an hour. They prepared to use the cutter on the steel net, but at that moment, the barrier was lowered to allow a destroyer to enter, so the silent intruders slipped in also.
Explosive charges were placed on two ships, and the human torpedoes headed back for the point at which they had entered the harbor. One of the British depth charges killed the two Italians.
Two weeks later, the bodies of Visintini and his companion were found inside Gibraltar Harbor. However, the existence of the top-secret Olterra base, located only a stone’s throw from one of Britain’s most crucial fortresses, had not been compromised.
With Gibraltar defenses on full alert against future penetrations of the harbor, Commander Pierleoni, the director of sabotage operations from his post as a diplomat in Barcelona, realized that a change in human-torpedo tactics was necessary. Ships in the open anchorage around the Rock now would be targeted.
In the weeks ahead, numerous human-torpedoes from the Olterra damaged ships at anchor and sunk two of them. Then, on the night of August 3, 1943, a pig with Lieutenant Commander Ernesto Notari and his number-two man, Petty Officer Gino Giannoli astride, were beneath their target, a seven thousand- ton U.S. cargo ship Harrison Grey Otis. Giannoli fixed the fivehundred- pound charge to the vessel and the pig suddenly went berserk. It plunged 110 feet deep (three times the maximum depth in training). Then the pig rushed upward and broke the surface.
Meanwhile, Giannoli had been thrown from his mount and surfaced on the far side of the ship. Thinking that Notari had been killed, the petty officer shivered in the water for nearly two hours. Then he shouted for help and the startled crew of the Harrison Grey Otis hauled him aboard.
At the same time, Ernesto Notari, although semiconscious, was still astride the pig. When his head cleared slightly, he saw that, amazingly, the engine was still running. Thinking that Giannoli was dead, he decided to make his getaway on the pig. For more than an hour, his steel mount edged through the water at three miles per hour. He was fearful that the phosphorescent wake would attract the attention of the crew of a British patrol boat.
However, the gods of underwater saboteurs smiled on Notari. A school of frolicking porpoises accompanied him all the way back to the Olterra, providing perfect cover for his wake.
Back on the Harrison Grey Otis, Gino Giannoli was being interrogated by British officers when the charge he had attached exploded on the other end of the ship. The engine room was badly damaged, putting the cargo vessel out of service for many weeks.
Minutes later, the handiwork of other human-torpedoes that had taken part in that night’s operation echoed over the seascape and up towering Gibraltar. A blast broke in two the ten-thousand-ton Norwegian tanker Thorshovdi, flooding the bay with a million gallons of oil. The six-thousand-ton British ship Stanridge was rocked by a third blast.
Gino Giannoli became a prisoner of war, but all the other Italians got back to the Olterra safely. However, the young petty officer would not hold a POW status for long. On September 29, 1943, Italy surrendered and joined the Western Allies, thereby converting Giannoli from a POW to a partner with the British.