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Operazione Golfo di Alessandria 1

August 12th, 1940 – August 22nd, 1940
Operazione Golfo di Alessandria 1
Objectives
  • Attack British warships in the Harbour of Alexandria, Egypt.
Operational Area
Alexandria, Egypt,  Harbour
Alexandria, Egypt, Harbour
Bay of Ain El Gazala, also known as Menelao Bay, in the Gulf of Bomba.
Bay of Ain El Gazala, also known as Menelao Bay, in the Gulf of Bomba, Lybia.
Allied Forces
  • Three British Swordfish torpedo bombers, H.M.S. Eagle, operating Ma’aten Bagush near Sidi Barrani, Egypt.
Axis Forces
  • Adua-class Submarine Iride
  • Spica-Class Torpedo Boat Calipso
  • Motorship Monte Gargano
  • Tug Egadi
  • Tug Luigi Rizzo.
  • 1° Flottiglia MAS
    • Commander of the Mission: Capitano di Vascello Mario Giorgini
    • Tenente di Vascello Gino Birindelli (Siluro a Lenta Corsa 1)
    • Capo di 2a Classe Damos Paccagnini (Siluro a Lenta Corsa 1)
    • Tenente di Vascello Alberto Franzini (Siluro a Lenta Corsa 2)
    • Sergente Giovanni Lazzaroni (Siluro a Lenta Corsa 2)
    • Capitano Teseo Tesei (Siluro a Lenta Corsa 3)
    • Sergente Alcide Pedretti (Siluro a Lenta Corsa 3)
    • Capitano Elios Toschi (Siluro a Lenta Corsa 4)
    • Capo di 2a Classe Enrico Lazzari (Siluro a Lenta Corsa 4)
    • Sottotenente di Vascello Luigi Durand de la Penne (Reserve)
    • Operaio Militare Pietro Biradelli
    • Four Siluro a Lenta Corsa’s
Operation

In July 1940, Admiral De Courten supervises an exercise of the 1° Flottiglia MAS at Bocca di Serchio and orders immediate action against British naval forces in the Mediterranean. During the exercise, he stresses the strategic importance of targeting British warships to disrupt their dominance in the region. The Italian navy faces growing pressure to innovate as traditional methods, such as aerial and submarine attacks, fail to yield decisive results against heavily defended British ports. Admiral De Courten highlights the potential of Siluri a Lenta Corsa of the 1° Flottiglia MAS, which offer a stealthy and unconventional approach to naval warfare.

On August 10th, 1940, Supermarina, the headquarters of the Regio Marina, issues orders to proceed with Operazione Golfo di Alessandria. An attack on the British fleet in Harbour of Alexandria, Egypt. Alexandria Harbour, located in Alexandria, Egypt, is one of the most significant ports in the Mediterranean. It serves as a critical maritime and military hub due to its location on the southern coast of the Mediterranean Sea, near the strategically vital Suez Canal, which connects the Mediterranean to the Red Sea and Indian Ocean. Alexandria Harbour consists of the Inner Harbour: The protected part of the port, used for docking warships, supply vessels, and commercial ships. It is shielded by breakwaters and is equipped with multiple berths for naval and civilian operations and the Outer Harbour: The larger, less protected area used for anchoring larger vessels awaiting entry into the inner harbour. The harbour is accessed through narrow channels, which are well-defended during wartime, including anti-submarine nets, minefields, and patrols.

During World War II, Alexandria Harbour is a major base for the Royal Navy’s Mediterranean Fleet. Its proximity to key conflict zones, including North Africa, Malta, and the Eastern Mediterranean, makes it a central hub for Allied operations. Alexandria serves as the headquarters for the British Mediterranean Fleet, coordinating naval engagements, convoy protection, and anti-submarine warfare in the region. The harbour facilitates the movement of troops, fuel, ammunition, and other vital supplies for campaigns in North Africa, particularly the Western Desert Campaign.

Admiral Cavagnari’s operational orders for Iride and its supporting vessels outline a precise and methodical plan for their mission. According to these instructions, the submarine Iride departs La Spezia on the morning of August 12th,1940. Following coastal routes, it is to arrive in Messina by 19:00 on August 14th, 1940, covering a distance of approximately 1,100 kilometres. Upon reaching Messina, Iride refuels completely with water and diesel, remaining there until receiving further instructions via a coded dispatch from Supermarina, transmitted through Marina Messina. These instructions, expected on August 16th, 1940, will specify the departure time for Menelaus Bay.

If no additional routing details are provided, Iride is to navigate from Messina to Menelaus Bay, a journey of approximately 1,000 kilometres. It will initially follow a coastal route past Ras Aamer, before transitioning to covert navigation through deeper waters, avoiding potential British minefields along Cyrenaica. The submarine is scheduled to arrive in Menelaus Bay on the morning of August 21st, 1940.

Simultaneously, the supporting torpedo boat, later identified as Calipso, departs La Spezia in the afternoon of August 16th, 1940. After embarking personnel, equipment, and the Siluro a Lenta Corsa’s from the 1° Flottiglia MAS’s training centre at Bocca di Serchio, it takes a deep-water route via the western edges of Capraia, Elba, and Corsica to reach Trapani, approximately 760 kilometres away, by the afternoon of August 18th, 1940. There, it refuels and departs for Tripoli following a coastal route via Pantelleria and Kerkeflah, covering another 570 kilometres. Upon arrival in Tripoli on August 19th, 1940, Calipso continues to Menelaus Bay, coordinating its arrival to coincide with Iride on the morning of August 21st, 1940.

At Menelaus Bay, mooring points are prearranged by the Port Office of Marina Tobruk. Calipso anchors at the most suitable location based on weather conditions, while Iride comes alongside to begin transferring the Siluro a Lenta Corsa’s. Provisions are made for refuelling both vessels during their stay, with Iride requiring an additional five tonnes of water, supplied by Calipso. Once the transfer is complete, Calipso is instructed to proceed to Tobruk for resupply.

Supermarina’s detailed instructions specify the execution of Operazione Golfo di Alessandria 1. Iride departs Menelaus Bay at dawn on August 23rd, 1940, navigating covertly to the operation’s staging area using designated waypoints. The submarine is to submerge upon reaching its target area, reserving half its underwater capacity for operational flexibility. The Siluro a Lenta Corsa’s will disembark from Iride at a specified point, with 30 minutes allocated for deployment. Following this, Iride will withdraw to its starting point, surfacing briefly to recharge before continuing its return journey to Menelaus Bay under cover.

The mission prioritises attacking battleships, aircraft carriers, and cruisers, with specific targets assigned by Capitano di Fregata Giorgini. To support this, daily aerial reconnaissance over Alexandria begins on August 20th, 1940, providing updates on the British fleet’s presence and mooring arrangements. Communications adhere to strict protocols, utilising a specialised code for transmissions. No secret documents, other than those necessary for communication, are permitted aboard Iride during the mission.

The mission is scheduled for the moonlit nights of August 26th, 1940, to August 27th, 1940, with fallback dates extending to August 29th, 1940, to August 30th, 1940. If delays prevent execution within this timeframe, the operation will be postponed. The Siluro a Lenta Corsa’s are fitted with 225-kilogram warheads and time fuses set for two hours, with adjustable settings based on situational requirements. Each Siluro a Lenta Corsa is crewed by two personnel, equipped with diving suits and identification cards, and under orders to destroy their craft near French warships if forced to abandon the mission.

Supermarina’s comprehensive planning reflects the operation’s significance, detailing every aspect from navigation and mooring to reconnaissance and attack priorities. The meticulous coordination between Iride, Calipso, and supporting forces is critical to the mission’s success.

The mission also relies on the support of the motorship Monte Gargano, stationed in the Gulf of Bomba. This vessel provides logistical aid, ensuring the smooth transfer of personnel and equipment between Calipso and Iride. The men involved in Operazione Golfo di Alessandria 1 include those in leadership, Siluro a Lenta Corsa operators, reserves, and support crews. The mission is led by Capitano di Vascello Mario Giorgini, who oversees the operation, with Tenente di Vascello Francesco Brunetti serving as the commanding officer of the submarine Iride.

The Siluro a Lenta Corsa operators assigned to the mission are Tenente di Vascello Gino Birindelli and Secondo Capo Damos Paccagnini (Siluro a Lenta Corsa 1), Tenente di Vascello Alberto Franzini and Sergente Giovanni Lazzaroni (Siluro a Lenta Corsa 2), Capitano Teseo Tesei and Sergente Alcide Pedretti (Siluro a Lenta Corsa 3), and Capitano Elios Toschi and Secondo Capo Enrico Lazzari (Siluro a Lenta Corsa 4).

The reserve for the mission is Sottotenente di Vascello Luigi Durand de la Penne and Operaio Militare Pietro Biradelli is coming along for technical support.

Summoned to Rome for discussions regarding Operazione Golfo di Alessandria 1, Capitano di Vascello Mario Giorgini reportedly advises against immediate action, citing the unpreparedness of the equipment. While the training of personnel has reached an acceptable level of proficiency, the condition of the Siluro a Lenta Corsa’s is cause for significant concern. Since large-scale production of the improved second-series Siluro a Lenta Corsa’s has yet to commence, it is decided to rely on older prototype models, which primarily have been used for training purposes. These prototypes are notorious for their frequent mechanical failures, making them less than ideal for operational deployment.

To mitigate these issues, four of the best-preserved prototypes are selected for the mission. These undergo extensive overhauls at the La Spezia Arsenal, with repairs completed by the end of July. Despite the maintenance efforts, the Siluro a Lenta Corsa’s are assessed to be in a condition described as “good, but not perfect.” Persistent issues with the trim pumps and other minor defects mean the equipment is still prone to potential malfunctions during the mission.

The Iride relies on a rudimentary system for transporting its Siluro a Lenta Corsa’s. This system consists of two pairs of saddles mounted directly on the deck, with two positioned forward of the turret and two aft. The Siluro a Lenta Corsa’s are secured to these saddles using halyards, a method that significantly restricts the submarine’s operational capabilities.

This rudimentary setup imposes a strict depth limit on the Iride. The maximum safe diving depth is limited to 30 metres, as greater depths would subject the exposed Siluro a Lenta Corsa’s to pressure damage. Consequently, the planned navigation route from the Gulf of Bomba to Alexandria must be conducted at or near this shallow depth, leaving the submarine more vulnerable to aerial detection. In contrast, the cylindrical containers adopted by later approach submarines are pressurised, allowing them to safely descend to depths up to three times greater without risking damage to the Siluro a Lenta Corsa’s. This improvement significantly enhances both operational flexibility and stealth capabilities.

Some evidence suggests that the Iride was originally intended to be equipped with these pressurised containers. However, the shipyards in La Spezia reportedly failed to complete the containers in time for their installation, forcing the use of the less effective saddle system for Operazione Golfo di Alessandria 1. This limitation places additional constraints on the mission, increasing the risks for the submarine and its crew.

From the beginning of planning, concerns are raised about using the Gulf of Bomba as the staging ground for Operazione Golfo di Alessandria 1. Its proximity to Alexandria provides a logistical advantage compared to Benghazi, but its lack of defences and facilities make it highly vulnerable. Tobruk, a closer and more fortified alternative, is dismissed due to its exposure to air raids, even though it offers stronger anti-aircraft protection. The Gulf’s remoteness, while offering an element of secrecy, creates significant risks if British reconnaissance discovers the presence of Italian vessels.

Capitano di Vascello Mario Giorgini warns of the dangers posed by the location. He highlights the exposure of Cyrenaica to British airpower, noting that Sidi el Barrani’s forward airstrip is only 280 kilometres away, just over an hour’s flight for a Swordfish torpedo bomber. The likelihood of British reconnaissance flights over the area is high, and the sight of Italian ships in this infrequently used anchorage would undoubtedly draw British attention. Giorgini emphasises the particular vulnerability during the critical transfer of the Siluro a Lenta Corsa’s from the Calipso to the Iride. This process, involving both crews and requiring trim tests of the submarine and functionality tests of the Siluro a Lenta Corsa’s at different depths, must be carried out in daylight, making the vessels highly susceptible to an attack.

Giorgini proposes an alternative, suggesting that the operation be staged from an island in the Dodecanese. While this option would increase the Iride’s navigational distance for its covert approach to Alexandria, it would offer greater safety. However, this suggestion is dismissed. Additionally, some accounts suggest that Tenente di Vascello Francesco Brunetti, commander of the Iride, also expresses doubts about the choice of Menelaus Bay. He views the location as dangerously exposed to air attacks and reportedly works to complete the transfer as quickly as possible to minimise the time spent in what he perceives as a hazardous area.

Despite these reservations, the decision to stage the operation from the Gulf of Bomba stands, primarily due to its strategic proximity to Alexandria. The Gulf of Bomba, a large bay open to the northeast, features two distinct inlets: one to the northwest and another to the southeast, known as Menelaus Bay. Menelaus Bay, unlike the other inlet, has a sufficiently deep seabed to permit the entry and mooring of ships. Additionally, the small island of El Maracheb, located just east of the bay, provides limited shelter from winds and rough seas.

In the northern part of the Gulf of Bomba, near the mouth of the Wadi et-Tmimi, lies a modest Italian seaplane base. This base, used by the 143ª Squadriglia Ricognizione Marittima of the Regia Aeronautica, also referred to as the Menelaus Squadron, is equipped with obsolete CANT Z.501 seaplanes. The facilities are minimal, consisting of a single hut serving as a canteen and a few tents. Nearby, a dirt airstrip is used for fighter operations. Defensive measures are limited to a few anti-aircraft machine guns. Because of the bay’s exposure to enemy air and naval attacks, the seaplane base is rarely used for regular operations. Aircraft from the 143ª Squadriglia Ricognizione Marittima are frequently relocated to safer bases, leaving the area primarily used for refuelling and as a stopover for transferring seaplanes.

The Gulf of Bomba is typically avoided by Italian warships. The area lacks proper docking facilities, such as jetties, mooring posts, or buoys, forcing vessels to rely on anchoring, which is unreliable due to exposure to northeast and southeast winds, including the strong libeccio winds. Assistance for ships is virtually nonexistent, and the lack of Italian naval activity in the area means that British reconnaissance aircraft rarely patrol over the bay.

Despite the less-than-ideal circumstances for the operation, Supermarina assesses the conditions as sufficient and gives final approval for Operazione Golfo di Alessandria 1 to proceed. This decision reflects their eagerness to deliver a decisive and impactful blow to British naval forces, even at the cost of relying on equipment and preparations that are not entirely optimal. With the plans set, the stage is fully prepared for the mission to commence.

August 12th, 1940

The submarine Iride, departs La Spezia, Italy.

August 14th, 1940

Following the coastal routes, the submarine Iride reaches Messina at 19:00. After refuelling, it remains in port awaiting further orders.

At 11:00, the Supermarina, headquarters of the Regio Marina, transmits a coded teletype dispatch authorising the continuation of its journey to Libya. The Iride departs Messina at 16:00 that same day, navigating along the coast to Cape Spartivento. At 20:30, it alters its course, heading directly toward the Gulf of Bomba.

The Supermarina had issued revised navigation instructions due to intelligence reports indicating British mines along the Cyrenaican coastline. Instead of the planned route hugging the coast, which included a stop at Ras Aamer before continuing to Menelaus Bay, the submarine follows a safer path through deeper waters to avoid potential minefields. The Iride completes its transit to the Gulf of Bomba under the cover of darkness without encountering any unusual incidents.

August 17th, 1940

The Torpedo Boat Calipso departs La Spezia, carrying the Siluri a Lenta Corsa’s, diving suits, breathing apparatus, other essential equipment and the personnel assigned to Operazione Golfo di Alessandria 1. This equipment and team had been loaded on the evening before at Bocca di Serchio, the training centre of the 1° Flottiglia MAS. The vessel makes refuelling stops in Trapani, Sicily and Benghazi, Libya.

August 18th, 1940

Auxiliary vessel Monte Gargano sails from Benghazi to the Bay of Bomba

August 21st, 1940

The Iride arrives in the Gulf of Bomba during the morning, mooring in Menelaus Bay near Ain el-Gazala, between the coastline and the island of El Maracheb. The Port Office of Marina Tobruk had prepared three mooring points specifically for the submarine. At 06:45, the submarine Iride sights the torpedo boat Calipso positioned aft of its starboard side.

Also present in Menelaus Bay is the auxiliary vessel Monte Gargano which arrived some time earlier. Several requisitioned fishing boats are also stationed in the area, playing a logistical support role. The Calipso and the Iride both enter the bay within minutes of each other, between 08:15 and 09:00, though one account suggests they may have arrived closer to 10:00. Together, these vessels anchor in the secluded waters of Menelaus Bay, preparing for the next phase of the operation.

Acting on orders from Capitano di Fregata Giorgini, the Iride moves alongside the Calipso by 09:00 to initiate the transfer of materials belonging to the 1° Flottiglia MAS. Shortly afterward, the Iride shifts approximately 250 metres east of the Calipso and drops anchor.

A motor sailer dispatched by Admiral Bruno Brivonesi, the maritime military commander of Libya, arrives shortly after. Brivonesi, who is overseeing the operation from aboard the Monte Gargano, provides directions for the Iride and Calipso to reposition themselves. At 11:30, the Iride weighs anchor once more and moves to its final anchorage near El Maracheb, settling approximately 300 metres north of the Calipso. Further north in the Gulf of Bomba, unrelated to Operazione Golfo di Alessandria 1, a steamer supplying the seaplane base and airfield at El Tmimi is anchored, along with three motor sailers unloading its cargo. These vessels remain uninvolved in the operation.

Later that morning, the commanders, Tenente di vascello Brunetti of the Iride, Tenente di vascello Zambardi of the Calipso, and Capitano di Vascello Giorgini of the 1° Flottiglia MAS, travel to the Monte Gargano aboard a small boat to meet with Admiral Brivonesi. During the meeting, plans are finalised for transferring the Siluro a Lenta Corsa from the Calipso to the Iride and for conducting sea trials to confirm the correct positioning of the Siluro a Lenta Corsa’s on their saddles. It is agreed that, to allow the crews of both vessels some rest and to coordinate further with the Libyan Air Force command on reconnaissance missions over Alexandria, the material transfer and trials will be postponed until the following day.

The commanders also discuss intelligence updates. A car is sent immediately to the headquarters of Marshal Rodolfo Graziani, commander-in-chief of the Italian forces in Libya, to verify reports from aerial reconnaissance over Alexandria earlier that morning. Confirmation arrives later, either from Graziani or directly from Rome, indicating that the British Mediterranean Fleet remains in port.

During the meeting, Tenente di vascello Zambardi and Capitano di Vascello Giorgini recount an encounter the Calipso had with a surfaced submarine at 03:15 the previous night near Ras Hilal. While navigating from Benghazi to Bomba, the Calipso had refrained from engaging the vessel, assuming it was the Iride, which was believed to be heading for Ras Aamer. However, Tenente di vascello Brunetti explains that the Iride had followed a different route under superior orders and could not have been the submarine sighted. It is determined that the Calipso had unknowingly encountered a British submarine. This information is immediately relayed to Marilibia and the Air Force, prompting a hunt for the enemy submarine. An officer from the Calipso is sent to the Menelaus seaplane base to coordinate efforts.

Following the meeting, Capitano di Vascello Giorgini travels personally to Cyrene and then to Derna. He coordinates with the High Command of the Libyan Air Force to finalise plans for an aerial reconnaissance mission over Alexandria the next day. The mission aims to confirm the presence and precise positioning of the British fleet in the port, critical to the success of Operazione Golfo di Alessandria 1.

Meanwhile, during the afternoon, six Bristol Blenheim bombers from the No. 55 Squadron of the Royal Air Force, though some accounts refer to them as part of the No. 211 Group of the Desert Air Force, conduct a bombing raid targeting the Tmimi airfield and the Menelaus seaplane base near the bay of the same name. This mission is unrelated to the Operazione Golfo di Alessandria 1. However, during their return flight to their base at Dakheila, shortly after 13:00, the British pilots notice an unusual cluster of naval vessels in the Gulf of Bomba.

As the bombers head back, three of the aircraft break away from the formation to investigate further. They conduct a cautious overflight of El Maracheb and the Italian ships stationed in the area. The aircraft maintain their distance, avoiding any engagement, and eventually veer left to rejoin the main formation before continuing to Dakheila.

Upon arrival at their base, the Blenheim crews report their observations to their superiors. They describe sighting a submarine and a torpedo boat in the waters of the Gulf of Bomba. This report immediately raises suspicions among the British commanders. The gulf, typically deserted and rarely frequented by Italian naval vessels, has never hosted such an unusual concentration of ships. Recognising the significance of the discovery, the British commanders decide to investigate further, confirming the very fears that Capitano di Vascello Giorgini and Capitano di Corvetta Brunetti had harboured.

August 22nd, 1940

At 07:00 in the morning, a British Short Sunderland reconnaissance seaplane from the no. 230 Squadron of the Royal Air Force, which had taken off at dawn from the seaplane base at Port Said, arrives over Menelaus Bay. Its mission is to verify the reports from the previous day’s Blenheim bombers regarding unusual naval activity in the Gulf of Bomba. Upon reaching the skies above the Italian ships, the Sunderland conducts an extended reconnaissance, drawing intense anti-aircraft fire from the vessels below. Despite the barrage, the aircraft remains unharmed and successfully gathers the necessary intelligence. After completing its observations, it withdraws undisturbed to the east, returning to base without incident.

Before the Sunderland even completes its flight, it radios back a detailed confirmation of the ships’ presence in the bay at around 08:00. The reconnaissance report identifies five vessels at anchor: a destroyer (in reality the Calipso), two submarines (mistakenly identified instead of one), a support ship (the Monte Gargano), a supposed tanker (likely confused with a previously reported steamer), and several motor sailers. The crew also provides precise information on the position of each target.

This confirmation is precisely what the British command has been waiting for. At 10:38, three Fairey Swordfish torpedo bombers from the No. 824 Squadron of the Fleet Air Arm take off from Sidi Barrani airfield to attack the Italian ships in Menelaus Bay. The No. 824 Squadron is usually assigned to the aircraft carrier H.M.S. Eagle, but, following a request by the Air Officer Commanding, Western Desert, the squadron had temporarily detached three Swordfish to a land base at Maaten Bagush. This base, approximately 160 kilometres west of Alexandria and 320 kilometres east of Tobruk, was selected to ensure rapid-response capabilities against Italian coastal shipping in Cyrenaica. The decision to establish this detachment had been made earlier in August by Admiral Andrew Cunningham, commander of the Mediterranean Fleet, in coordination with Air Marshal Arthur Longmore, commander of British air forces in the Middle East. Under their agreement, operational control of the aircraft had been delegated to Air Commodore Raymond Collishaw, the Royal Air Force’s commander in Egypt and the Western Desert, based at Maaten Bagush.

During the morning, the three Swordfish are scrambled from Maaten Bagush on General Collishaw’s orders as soon as the Sunderland’s reconnaissance report is received. Due to the distance from their target, they make an intermediate stop at Sidi Barrani, located roughly 240–290 kilometres from the Gulf of Bomba, to refuel. Even with this stop, the Swordfish are fitted with auxiliary fuel tanks to extend their range.

After departing Sidi Barrani, the Swordfish fly approximately 80 kilometres offshore to approach the target from the sea, intending to surprise the Italian ships from an unexpected direction. They continue parallel to the Libyan coastline until 11:30 when they reach the Gulf of Bomba. At this point, they turn towards the entrance to Menelaus Bay to initiate their attack.

The conditions for the operation are ideal. The sky is mostly clear, with minimal cloud cover (1/8), and the sea is calm, offering excellent visibility. A light breeze blows from the southeast, and atmospheric pressure is beginning to drop slightly. These factors create near-perfect conditions for the Swordfish to carry out their assault on the unsuspecting Italian vessels below.

That morning the Iride is anchored in the bay of Ain El Gazala, also known as Menelao Bay, in the Gulf of Bomba, Libya. She is positioned at coordinates 32° 16’N, 23° 13’E, approximately 2.4 kilometres from Ras Megara. At 09:00, the submarine Iride pulls alongside the support ship Calipso to transfer two Siluri a Lenta Corsa’s and five crates containing diving suits, specialised breathing apparatus, and other underwater equipment. The operation concludes by 11:20. During this time, according to one account, Iride also takes on diesel fuel. Ammiraglio Brivonesi, aboard the Monte Gargano, invites the men of the 1° Flottiglia MAS to a celebratory toast, offering them good wishes for their mission’s success.

Following these preparations, Capitano di Vascello Giorgini instructs Tenente di Vascello Brunetti to conduct a test dive. The submarine is tasked with descending to 30 metres for two hours to test the release mechanisms of the Siluri a Lenta Corsa, ensuring they function properly under such pressure. Three personnel from the 1° Flottiglia MAS, Birindelli, Pedretti, and Lazzaroni, along with electrician Biradelli, are transferred to the Iride for the test, while the rest of the flotilla remains aboard the Monte Gargano.

The Iride starts its starboard diesel engine and moves away from the anchorage near El Maracheb. Meanwhile, Calipso refuels from the Monte Gargano before mooring approximately 100 metres off its port side. Before submerging to 30 metres, the Siluri a Lenta Corsa’s need to be secured in their operational positions on the submarine’s saddles. To facilitate this, the Iride surfaces with its deck submerged about 1 metre below the waterline, making the placement of the Siluri a Lenta Corsa’s easier due to buoyancy. The submarine relocates to a seabed approximately 14 metres deep, 2.8 kilometres from Ras Megara, ensuring calm waters to avoid damaging the Siluri a Lenta Corsa’s.

At the designated location, the Iride stops its engine and partially floods its forward ballast tank to achieve the required depth. Lookouts maintain vigilance, weapons are manned, and anti-aircraft machine guns are ready in case of an air attack. Tenente di Vascello Brunetti, Tenente di Vascello Birindelli, and navigation officer Tenente di Vascello Ubaldelli remain on the bridge to oversee operations.

At 11:56, the Iride raises the air raid alarm after spotting three aircraft flying westward at an altitude of 30–40 metres, approximately 3.5 kilometres away. These aircraft are identified as Fairey Swordfish from the 824th Squadron of the Royal Navy. At this moment, the submarine’s deck remains submerged by about 1 metre of water. The two forward-mounted Siluri a Lenta Corsa are already secured, but work on the stern-mounted Siluri a Lenta Corsa is ongoing.

In shallow waters, a rapid dive is impossible. Tenente di Vascello Brunetti orders the submarine’s cannon and machine guns to engage and the electric motors to full power, as the diesel engines are disengaged during diving preparations. Most air vents are closed, except for those at the extreme bow and stern, and watertight hatches are sealed, though the turret hatch reportedly remains open.

Descending from 30 metres to just 10 metres, the Swordfish approach in a V formation. The lead aircraft, piloted by Captain Oliver Patch, targets the Iride, while the other two aim for Calipso and Monte Gargano. As they close in, the Iride and its companion ships open fire with anti-aircraft weapons. Despite evasive manoeuvres by Captain Patch, his Swordfish releases its torpedo from a distance of 270 metres. Tenente di Vascello Brunetti attempts to turn the submarine’s bow toward the incoming torpedo to reduce the target profile, but the distance is too short. The torpedo strikes the Iride near the turret, splitting the vessel in two.

The Iride sinks rapidly by the bow, leaving part of the stern visible above water for a few minutes before vanishing entirely. Of the 50 men aboard, 14 are on the deck during the attack. Two are killed by machine-gun fire from the aircraft, while the remaining 12, including Tenente di Vascello Brunetti, are thrown into the sea.

Simultaneously, the Calipso and Monte Gargano are also targeted. One torpedo narrowly misses the Calipso and detonates on the shore, while another strikes the Monte Gargano, causing it to capsize and sink. Remarkably, no fatalities occur among the Monte Gargano’s crew. The Calipso, suffering minor shrapnel damage.

After the Iride sinks, rescue efforts begin immediately, as the submarine lies in shallow waters between 16 and 20 metres deep. There is hope that some compartments remain intact and that survivors are trapped inside. However, the underwater breathing equipment essential for such an operation sinks with the Iride, forcing the rescuers to rely on improvised methods and sheer determination.

The initial dives are carried out without proper equipment. Men from the 1° Flottiglia MAS, including Capitano del Genio Navale Teseo Tesei, Capitano del Genio Navale Elios Toschi, and others, repeatedly dive into the wreck, descending progressively deeper. Tesei, known for his incredible lung capacity, makes three dives and eventually spots the submarine. The Iride is broken in two, with the bow section tilted 90 degrees to its port side, and the stern upright on the sandy seabed. Air is still escaping from some hatches, but it is clear that the aft torpedo room might remain dry.

The divers bang metal tools against the hull to communicate with any survivors. For hours, there is no response. Then, at 18:25, during one of Tesei’s dives using a Davis breathing apparatus, faint knocking is heard from inside the aft torpedo room. Stronger banging follows, and the voices of survivors become audible through the hull. Nine men are alive, trapped but communicating with the rescuers.

The divers immediately relay the news to the surface, and the rescue effort intensifies. Throughout the evening and night, divers including Tesei, Toschi, Birindelli, and Luigi Durand de la Penne work tirelessly. Without proper wetsuits, they endure cold waters, and their breathing equipment provides only 20 minutes of autonomy. They dive repeatedly, using hammers, chisels, and sledgehammers to clear debris blocking the aft hatch. After every 20-minute dive, they surface to replace their breathing tanks and resume the gruelling work.

Meanwhile, a fishing vessel is requisitioned to act as a support platform. During the night, as the divers regroup, two of the trapped men panic. Ignoring warnings to stay calm, they attempt to use the emergency escape chamber, damaged during the explosion. Flooding the chamber, they drown inside, taking the last of the Davis breathing apparatus with them.

August 23rd, 1940

On the morning, more equipment arrives from Tobruk, including a rescue pontoon and an air pump. Divers pump fresh air into the torpedo room to sustain the survivors, who report worsening conditions. The air is stale, and there are faint traces of chlorine from seawater contamination. Time is running out.

By midday, the divers manage to clear the debris blocking the aft hatch. Using cables secured to the fishing vessel, they pull the hatch free. Inside, they find the bodies of the two men who drowned during the night. The seven remaining survivors are alive but weak and agitated.

To extract the survivors, the rescuers devise a risky plan. They instruct the men to gather near the ceiling, where a pocket of air will form as the compartment is gradually flooded to equalise pressure with the outside. The men are told to exhale slowly during their ascent to avoid fatal injuries from expanding air in their lungs. One by one, they will be guided through the escape chamber and to the surface.

At first, some survivors distrust the rescuers, fearing the plan will drown them. The divers issue an ultimatum: cooperate or risk being left behind. One survivor finally opens the internal hatch, allowing water to flood the compartment slowly. The rescuers begin guiding the survivors out.

The operation is harrowing. One by one, the men are brought to the surface, where they emerge unconscious but alive. Tragically, two of the seven succumb to traumatic embolisms shortly after surfacing, despite attempts at artificial respiration.

The rescue of the final survivor, 20-year-old electrician Luigi Sgariglia, becomes a defining moment. Unable to swim and paralysed by fear, Sgariglia refuses to attempt the escape. Durand de la Penne descends with a breathing apparatus, gives it to Sgariglia, and tries to lead him out. Sgariglia panics and uses up all the oxygen in the tank. De la Penne gives him his own breathing apparatus and physically pushes him through the escape chamber. De la Penne, now without air, ascends alone, pulling himself along a guide rope to the surface. Exhausted but alive, he emerges last, having saved Sgariglia’s life.

In total, five men are successfully rescued from the aft torpedo room. Combined with those thrown into the sea during the attack, 13 men from the Iride survive. Tragically, 31 of the crew lose their lives, including officers and petty officers.

Aftermath

The mission results in the loss of the submarine Iride, along with 33 crew members and the motorship Monte Gargano. This operation, despite its failure, underscores the bravery and technical ingenuity of the crew and operators involved. The tragedy prompts a comprehensive evaluation of Italian naval tactics and equipment. The findings from this mission lead to the design of more reliable Siluri a Lenta Corsa’s and improved transport systems, such as cylindrical containers, which allow submarines to carry these craft at greater depths, up to 90 metres.

The rescue operation, led by Luigi Durand de la Penne and supported by Teseo Tesei, becomes a defining moment in the development of Italian naval special forces. Their actions serve as a testament to the dedication and sacrifice inherent in the 1° Flottiglia MAS. Survivors of the attack and the Siluro a Lenta Corsa teams return to La Spezia, where they continue to train and refine their techniques for future missions.

Medaglie d’Argento al Valore Militare are awarded to Francesco Brunetti, Mario Giorgini, Gino Birindelli, Damos Paccagnini, Alberto Franzini, Giovanni Lazzaroni, Teseo Tesei, and Elios Toschi. Medaglie di Bronzo al Valore Militare are awarded to Luigi Durand de la Penne and Alcide Pedretti.

British intelligence takes note of the attack, recognising the potential threat posed by these innovative craft. The Gulf of Bomba incident influences subsequent British anti-sabotage measures, including reinforced harbour defences and the deployment of anti-submarine patrols.

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