M Class | Guide 396

With World War 1 well into its second year, the value of submarines was becoming more and more obvious. On top of this, the initial rush of orders to expand the Royal Navy's submarine fleet was now pretty much done with, and with the use of so many different types and sizes of submarine on both sides, it was felt that perhaps a more organised approach to future submarine construction was needed. Thus, a Submarine Design Committee was convened to look into six kinds of submarines, coastal, patrol, fleet, cruiser, minelayer and monitor. The coastal and patrol types already existed in quite some numbers, the fleet type would be the K-class which was already under construction, the minelayer option was already in the process of being trialled as two E-class submarines were being converted, and that left the cruiser and monitor types. Although there was some interest in the cruiser type, the fact that the primary naval threat wasn't exactly all that far from British shores meant that the main immediate benefit of a cruiser type would just be long time spent on station, as opposed to being able to operate especially far away. The monitor type therefore took centre stage in initial development, it had been noted that a number of important targets had been missed when torpedoes had either been spotted and evaded, or the aim of the torpedo had been miscalculated in the first place. But torpedoes of the time usually needed to be launched at a range of under 1000 yards, which was almost bayonet range when it came to big naval guns. Rumours of a large man sitting in the shadows and citing that no one can outrun bullet remain unconfirmed. It was felt that a large naval shell delivered at almost unmissable range, especially if the sub rose up a stern of the target and sent the shell crashing in at almost waterline height through the stern of the ship, wrecking the rudder linkages, possibly damaging propeller shaft alleys and thanks to the lack of aft armour probably punching through quite a few compartments and possibly even into the engine room or magazines, would be a far surer way of sinking or at least crippling a target, which could then be finished off with torpedoes. This idea took hold after the monitor role of shore bombardment was quickly pushed into the background thanks to somebody realising that most of the German coastline was very shallow shoal water where a submarine could not submerge and even large surface ships at times had to wait for a high tide to reach into or leave some ports. There was a degree of debate as to whether a short calibre 12-inch gun with a 4 or 6-inch gun aft or a pair of 7.5-inch guns, one short barrelled with high explosive shells and the other longer with armour-piercing only shells, would be a better armament. There was also debate on whether to use the K-class style steam propulsion or revert to diesel-electric. And of course what size should this submarine be, an early sketch called for the 320ft long K-class hull to be used as a basis, then made wider and deeper, with a 40ft beam and a 15ft draft when surfaced. This would have given it a displacement of around 2,500 to 3,000 tonnes on the surface and about 4,000 tonnes underwater, which in turn would have made them the largest conventional submarines ever operated by the Royal Navy right down to the and on a par size-wise with the nuclear-powered HMS Dreadnought of the 1960s. These debates kept on going until the following year, with the final design ending up resembling a scaled-up J-class submarine hull with the power plant of an L-class, displacing just a little bit under 1,600 tonnes on the surface and a little bit under 2,000 tonnes when submerged. The armament consisted of a 12-inch .40 caliber gun mounted just forward of the conning tower, using spare guns that had been built for the formidable class pre-dreadnoughts, as two out of the three had been sunk, so there were a lot of spares going. There was a 3-inch anti-aircraft gun aft and four torpedo tubes forward, 18-inch in diameter in the first two submarines and 21-inch in diameter on the second two. With the K-class not really working out quite as well as they'd hoped, K-18 through 21 were cancelled and reordered as M-1 through M-4. The big gun could be elevated up to 20 degrees and traversed up to 10 degrees to port or starboard which did allow for a degree of aim adjustment so you didn't have to physically aim dead on with the entire submarine. The idea was that the gun would be pre-loaded with a flip-down watertight seal at the muzzle which was controlled from inside. The sub would stalk its target at periscope depth and then, thanks to an unusually large number of valves and pumps connected to the ballast tanks, surface within 25 seconds of the order being given with the gun pre-aimed. The gun would be remotely fired and then in just 15 more seconds the sub could be back at periscope depth, from which further options could be considered. To aid in this, a third periscope dedicated to gun control was added and a range finder was incorporated into one of the two regular periscopes. Once the enemy had been sunk or the sub had just moved away, reloading the gun could be accomplished on the surface in about 3 minutes. M-1 and M-2 were laid down in July 1916 with M-3 and M-4 following in December. They were soon paused out of concern that the Germans might build their own variety when they learned about the operation of these subs and of course the UK's coasts were far more vulnerable to attack from this kind of submarine but they were restarted after a few months. As a result of the delays, only M-1 entered service during the First World War but did not see any frontline action. M-4 was cancelled right after the end of the war and broken up for scrap on the slipway with M-2 and M-3 commissioning in 1920. Escaping the Washington Naval Treaty by a loophole that submarines gun armament for any future submarines, M-1 through M-3 operated until M-1 was lost in late 1925 during an exercise when she was accidentally rammed by a Swedish merchant ship. The other two were then put in reserve and reassigned to experimental service. M-2 had her gun and its mounting replaced by a hanger for a single folding seaplane and a crane. A couple of years later a catapult was added allowing you to directly launch the aircraft from the sub and the sub was now used as a long range fleet scout. Unfortunately in 1932 something went wrong while she was surfacing to launch her aircraft during another exercise and she sank with all hands. M-3 had her gun replaced by a very long superstructure which could hold a hundred mines turning her into a giant mine layer. Unfortunately the massive volume ruined what was otherwise a very well performing submarine hull and she was sold for scrap in 1932 with the lessons learned being applied to future mine laying submarines in the Royal Navy. That's it for this video. Thanks for watching. If you have a comment or suggestion for a ship to review, let us know in the comments below. 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