Early 1942, the Aian Sea in waters the Italian Navy believed it controlled. A typical gun action looked like this. A British T-class submarine breaks the surface. Sea water pouring off a hull designed to sink, not fight. Five men scramble forward through the spray to a stubby 4-in gun bolted to the deck.

 No armor, no shield, no overhead cover, just a crude pedestal mounting, a ready use ammunition locker, and a crew standing in the open on a deck perforated with holes so the boat can flood faster when it dives. The whole thing looks like it belongs on a fishing twler. From below, more men form a human chain, passing 47lb rounds hand over hand up through the conning tower.

 60 seconds after surfacing, the first round fires. Eight rounds later, a Greek Kayik loaded with German soldiers is burning from stem to stern. The submarine slides beneath the waves and vanishes. The entire action has taken less than 10 minutes. This ugly, exposed, dripping, wet arrangement of steel and brass would sink more axis shipping in the Mediterranean than most people realize.

Italy could punish submarines brutally with mines and escorts, and 13 T-class boats would never return. But against the small, lightly defended coastal traffic that filled the Aian in low light windows at dawn, dusk, and at night, the deck gun created a deadly opportunity that Italian defenses could not close.

 To understand why a crude deck gun became one of the most cost-effective killing instruments of the Mediterranean War, you need to understand what the Royal Navy was facing in 1940 and 1941. Italy entered the war on June 10, 1940 with roughly 786 merchant ships over 500 tons totaling approximately 3.3 million gross registered tons.

 But Mussolini gave only 3 days warning. Around 212 ships, roughly 1.2 million tons, including 46 tankers, were caught outside the Mediterranean and immediately lost to seizure or internment. Italy was then entirely dependent on seaw routes to supply its forces in North Africa, Albania, Greece, and the Aian Islands. There was no overland alternative.

 An average of four concurrent convoys were at sea at any given time, running roughly 600 km westward around Sicily, then hugging the Tunisian and Libyan coast to Tripoli. The Royal Navy’s submarine force, operating primarily from Alexandria and Malta, was tasked with strangling those supply lines. Torpedoes were the primary weapon against large transports and warships.

But the Mediterranean and especially the Aian Sea was full of something torpedoes could not efficiently kill. Hundreds of small coastal vessels, cakes, schooners, felucas, coasters of 25 to 300 gross registered tons sailed between the Greek islands carrying German troops, ammunition, fuel, and supplies. A standard Mark 8 torpedo weighed approximately 3,450 lb over a ton and a half, carrying a 365 kg Torpex warhead.

 Using one against a 68 ton wooden sailing boat was absurd, with only 16 or 17 torpedoes per patrol. Everyone had to be saved for high-v value targets. The submarines needed a cheaper way to kill small ships. They already had one. It was bolted to the deck. It looked terrible. And as one submarine ace later calculated, it averaged 10 tons of sunken enemy shipping for every single round fired.

The T-class was the largest class of oceangoing submarines in Royal Navy history. 53 were built in three groups between 1937 and 1945. Group one boats displaced 1,090 tons surfaced and 1,575 tons submerged, measured 275 ft long, and carried a crew of 59. Surface speed reached 15.25 knots on twin diesel engines producing 2500 brake horsepower.

The torpedo armament was formidable. Group 1 boats carried 10 torpedo tubes, all forward facing, including six internal bow tubes, two external bow tubes, and two external amid ships. This gave the T-class the largest forward salvo capability of any operational submarine ever built. But the weapon that concerns us sat forward of the conning tower, a 4-in 102 mm QF Mark12 or Mark 22 gun on an S1 pedestal mounting.

 According to Nave’s technical data, these were 40 caliber weapons with a barrel length of just over 4 m, firing fixed quickfiring ammunition, where the shell and cartridge case were integrated into a single round for faster loading. The standard shell weighed 31 lb with a complete round weighing between 47 and 52 lb.

 Muzzle velocity was 1,873 ft pers. The official rate of fire was 13 rounds per minute, though experienced gun crews could manage 15 to 18 aimed shots. Maximum range at the mount’s 20° elevation limit was approximately 10,450 yd, but combat engagements typically happened at 500 to 3,000 yd. At those ranges, against wooden hold vessels, the 4-in shell was devastating.

 The mounting weighed 5 tons and trained manually through roughly 240°. Five men crewed it, a gun captain who also set the sights, a gun layer handling elevation, a gun trainer handling traverse, a loader working the brereech, and an ammunition handler. Critically, there was no armor and no overhead protection.

 Only three late production boats received factory-fitted gun shields. Most crews fought completely exposed. Much of the conning tower structure was brass rather than steel to avoid compass interference, which meant even less protection than it appeared. Secondary armorament included 3.303in machine guns, originally Lewis guns and later vicers or brens, and from group 2 onward, a 20 mm ericon cannon mounted after of the conning tower.

 The initial ammunition allocation of 100 rounds proved completely inadequate for aggressive Mediterranean patrols. By the later stages of the war, T-class boats would forgo reload torpedoes entirely in favor of carrying additional gun ammunition. That single fact tells you everything about how central the deck gun had become.

 A gun action followed a precise sequence. At periscope depth, the captain identified the target, assessed threats from aircraft, escorts, and shore batteries, checked the seastate, and ordered gun action stations. The submarine blew main ballast tanks with compressed air and rose to the surface. The bridge party scrambled up first to scan for danger.

Then the five-man gun crew raced through the conning tower hatch and forward to the gun. Initial rounds came from a small waterproof reduse locker near the mounting, allowing fire to open before the full ammunition supply chain was established. Below decks, additional men formed a human chain, passing rounds from the magazine through the conning tower and up to the gun.

 A well- drilled crew could fire the first round within 60 to 90 seconds of the surface order. The vulnerability was acute. The submarine was a terrible gun platform. Low freeboard, significant rolling, waves washing over the gun crew. The deck itself was perforated with flooding holes. A single penetrating hit on the pressure hull could be fatal.

 Crash dive time from standard surface condition was 30 seconds. But with five men on the gun, more in the ammunition chain, and all hatches open, clearing the deck added critical time. Every second exposed on the surface was a second closer to disaster. Now, before we see how this performed in combat, if you’re enjoying this deep dive into British naval engineering, hit subscribe.

 It takes a second, costs nothing, and helps the channel grow. Right, let’s get into the combat record. HMS Turbulent under Commander John Linton compiled what may be the finest fighting record of any Royal Navy submarine. Arriving in the Mediterranean in February 1942, Turbulent completed 12 patrols from Alexandria and later Alers before her loss around March 6th, 1943.

 According to Linton’s Victoria Cross citation, he sank one cruiser, one destroyer, one hubot, and 28 supply ships totaling approximately 100,000 tons, and destroyed three trains by gunfire. In his final year, he spent 254 days at sea, was hunted 13 times, and evaded over 250 depth charges. His deck gun actions were prolific.

 According to compiled patrol records, on February 27, 1942, he surfaced north of Monvesia and sank the Kaika Guiosamos with 42 rounds at 3,000 yd, reportedly scoring six hits. On March 2 alone, he conducted three separate gun actions. First the Kaik Evangelistria, 22 rounds fired with 16 reported hits at 1,600 yd. Then Apostto, nine rounds, seven reported hits at,200 yd.

 Then Cheracleia at night, eight rounds at 500 yd. The following day he sank a Guillos dianios and fired on the Promos before checking fire when he realized the vessel was full of women. Though according to patrol reports, 10 were still killed and five wounded. By March 13, after sinking the Kaiik Anastasis at 400 yd, Turbulent had only one round of 4-in ammunition remaining.

 Beyond the Kayak campaign, Linton shelled the 271 ton Italian merchant Roser M from 4,500 yd with 39 rounds and most remarkably bombarded Italian railways and destroyed three trains with his deck gun. One of the most unusual feats in submarine warfare. Linton was lost with all 63 crew probably sunk by the Italian torpedo boat Adito south of Naples.

 HMS Torbay under Lieutenant Commander Anthony Mes produced equally extraordinary results. According to her patrol records, Tobay sank 17 merchant ships totaling 38,000 tons, five warships, and 24 sailing vessels during nine Mediterranean patrols. On her first patrol, the gun crew had literally never fired the weapon before.

 They learned fast. On July 4, 1941, Kaik sailing under German flags and loaded with troops were destroyed with 4in and Lewis gunfire. By July 9, with only 19 rounds remaining, Mus adapted his tactics. Stop them with one well- aimed round of the deck gun, clear the decks with the Lewis gun, then scuttle them with demolition charges.

 Fire opened on Kaiks loaded with petrol, ammunition, and German mountain troops, creating, according to crew accounts, such a fire that it was not possible to go alongside. But the action that earned Mia his Victoria Cross was not a gun action at all. On the night of March 4, 1942, he followed an enemy convoy into Corfu Harbor, charged batteries on the surface in full moonlight under enemy guns, then torpedoed two 5,000 ton store ships in the roadstead at dawn.

 Tobay then endured 40 depth charges during a 17-hour withdrawal through 30 mi of narrow patrolled channel. His first left tenant calculated the chances of getting in as fair, although the dice were heavily loaded against getting out again. HMS Thunderbolt, the rebuilt HMS Thetus, which had sunk during trials in 1939, killing 99 men, conducted at least six bombardments and gun actions under Lieutenant Commander Cecil Crouch.

 On September 10, 1941, she bombarded Fort Baroli at Certi in Libya and shelled a threemasted schooner at anchor with 11 rounds, scoring four hits and setting it ablaze before coming under fire from a shore battery. Her Jolly Roger displayed half a dozen vessels sunk by gunfire alongside seven torpedo kills. Thunderbolt was lost on March 14, 1943 to the Italian Corvette Sakona off Sicily.

 When her wreck was found in 1995, she was identified by the tally on her 4-in gun reading Thetus number 1027, her original haunted name. These actions were possible because of a critical Italian weakness. Italy entered the war with virtually no shipborne radar and almost no purpose-built anti-ubmarine escort vessels.

 According to analysis published by Commando Supreo, Italian warships relied on hydrophones and optical sightings for the first 18 months. Hydrophones were considered almost useless because ship engine noise disturbed acoustic search at anything above four knots. The goof radar had been under development since 1936, but was stalled by budget cuts and institutional indifference.

 After the disaster at Cape Matapan in March 1941, where Italian lack of radar proved catastrophic, interest revived, but radar adoption remained limited until late 1942 when the battleship Lator received one of the first operational shipboard sets by the armistice on September 8th, 1943. Guo radar installations across Italian warships reportedly numbered around 12.

 This technological blindness made Italian shipping, especially the small coastal craft filling the Aian, desperately vulnerable to surface submarines operating at dawn, dusk, and at night. The comparative picture reinforces just how effectively the British exploited these conditions. German type 7 Ubot carried an 8.

8 cm gun firing a 15 kg shell. The larger Type 9 boats mounted a 10.5 cm gun with a heavier 24 kg shell. Both were effective weapons. Italian submarines carried 100 mm guns that were intriguingly a licensed variant of a British design. The hardware was broadly comparable across all three navies. The difference was doctrine and environment.

German hubot used deck guns extensively in the early war to conserve torpedoes against lone Atlantic stragglers. But as Allied radar, convoy escorts, and armed merchant ships improved, surfacing became suicidal. From June 1943, Atlantic Yubot departed bases without deck guns on Admiral Dunit’s orders. Guns were removed to reduce drag and speed crash dives.

 The Mediterranean created the opposite dynamic. Calm seas made the submarine a far more stable gun platform than in the Atlantic. Though those same clear, shallow waters also made submerged submarines easier to spot from the air and escape after an action harder. Italian technological weakness meant submarines could surface with near impunity, and the abundance of small unarmed targets made the gun economically and tactically superior to the torpedo.

 A 31lb round costing pennies could sink a vessel that would have required a torpedo worth thousands of pounds. The strategic results were devastating. In late 1940 to early 1941, Italy lost roughly 6.6% of supplies shipped. By August 1942, the loss rate exceeded 30%. By October 1942, it reached 44%. An Italian Admiral T memorandum from August 1943 acknowledged plainly that Italy, having lost control of the Sicilian Channel and being confined to home waters, had by that point lost the war.

 By the armistice, 342 Italian freighters totaling approximately 1.3 million tons had been sunk, representing 60% of Italy’s total Mediterranean merchant tonnage. The cost was real. Of 53 T-class submarines built, 13 were lost in the Mediterranean. Over half fell to Italian minefields, the silent killer that no amount of aggression or seammanship could defeat.

 All seven Group 2 T-class boats were sent to the Mediterranean. Only Thrasher and Trusty returned. a 71% loss rate. Four Victoria Crosses were awarded to T-class Mediterranean crews, more than any other submarine class in the war. The deck gun itself did not survive the piece. Inspired by the revolutionary German type 21 submarine, the Royal Navy streamlined its surviving T-class boats for Cold War service.

 Deck guns were removed, conning towers replaced with streamlined sails, and the primary mission shifted from killing surface ships to intercepting Soviet submarines. HMS Andrew had a 4-in gun reinstalled in 1964 for the Indonesia Malaysia confrontation to counter blockade running junks. Her gun was fired for the last time in December 1974, making her the last British submarine to carry a deck gun.

 Think back to that image from the opening. Five men standing in the spray on a perforated steel deck, wrestling shells into a crude mounting with no armor and no protection. It looked wrong. It looked primitive. It looked like it had no business being on a submarine at all. But between 1940 and 1943, in the warm, calm, radar blind waters of the Mediterranean, that ugly 4-in gun and the aggressive captains who used it helped destroy 60% of Italy’s merchant fleet.

 Not through superior technology, but through the British willingness to bolt a gun to a submarine, surface in enemy waters, and fight it out in the open. The numbers prove it. The patrol records confirm it. And the 13 boats that never came home remind us what it cost. British engineering was not always elegant.

 Sometimes it was a crude gun on a wet deck fired by five men who knew that every second on the surface brought them closer to disaster. It worked anyway. That is the British war weapons