Submarine Warfare in World War II (WWII):
In WWII, submarines were widely used by both sides as the ultimate weapon of naval blockade, they sank large numbers of merchant ships and warships, which resulted in either paralyzing the enemy's military industry and war effort by causing severe shortages of war materials and products and preventing maritime troop transfers, or forcing the enemy to dedicate enormous resources to anti submarine warfare in order to prevent that from happening, resources which could otherwise be used in the enemy's main war effort.
Either way, the submarine was the classic weapon of the war of attrition; victory was achieved by the side which inflicted significantly more losses in men and material on the enemy than it suffered and the monthly ship tonnage loss count reflected the success or failure of a submarine; a submarine's ability to attack almost anywhere and anytime, in total surprise and with devastating results, makes it a highly efficient weapon, in which a small crew of less than 100 submariners can do more damage than 1000 sailors in a battleship and for a fraction of the cost; a larger anti-submarine force was required in order to efficiently counteract a submarine.
The submarine features made it the perfect blockade runner; it was capable of quietly smuggling secret agents and commandos, or small amounts of high importance cargo, to and from almost any enemy beach or blockaded harbour, making the submarine a useful intelligence and special forces vehicle.
WWII submarines had a limited underwater speed, range and endurance; therefore, they often sailed on the surface, especially at night, and only submerged when they had to, in order to avoid being detected and attacked; in the beginning, German submarines often made group night attacks while surfaced, like torpedo boats, but as RADAR and aircraft were more widely used to detect and attack submarines, they were forced to remain submerged most of the time; this led to new technical and electronic improvements, to significantly improve a submarine's underwater performance, and awareness of nearby danger.
German submarines were called Underwater Boats (U-boats) and their success in WW1 against British shipping was such that after its defeat Germany was not allowed to have any submarines; however in 1935, Germany began to build a submarine force, under the command of a former WW1 U-boat captain, Karl Doenitz; this brilliant, innovative and experienced submarine commander advanced submarine warfare to new heights; he trained highly skilled crews and captains and developed devastating new tactics such as the Wolfpack tactic which allowed a group of submarines to efficiently coordinate and concentrate their effort instead of fighting alone.
The Wolfpack tactic involved having a spread of submarines across a long stretch of ocean, in order to enhance their probability of detecting any passing enemy ships, and when a submarine detected a convoy of enemy ships, it reported its position and course to the other submarines and then followed the convoy instead of attacking it; meanwhile, the other submarines would regroup into a position ahead of the enemy convoy, and when ready would all attack it together, preferably at night; this tactic often overwhelmed, or even outnumbered, the convoy's anti-submarine escort and led to many of the ships being sunk.
The devastating use of such tactics by German U-boats and the systematic ongoing analysis of results and subsequent adaptation, made Doenitz and his submarines the most formidable enemy Britain had ever faced, more worrying even than the Luftwaffe; Winston Churchill stated that the only threat that really worried him during WII was the U-boat peril.
The only thing that saved Britain's Navy from being defeated early in the war by the German U-boats, were Doenitz's superiors; the German Navy, like the British Navy, was dominated by Admirals who served in warships and despite the successful experience of German U-boats in WW1 and the development of aircraft as a powerful weapon against surface ships, they kept the submarines force as a secondary arm of the Navy, in terms of budget allocation.
As a result, Hitler and Roeder, head of the German Navy, confidently rejected Doenitz' pre-war warnings that Germany had too few submarines to achieve their task of cutting Britain's maritime life line and instead of having around 300 submarines at the beginning of the war, which he had wanted, he only had 55 and only 12 of them could be active in the atlantic operations; the experienced Doenitz had calculated that with U-boats sailing to and from from the area of operations, U-boats used for training new crews and U-boats being resupplied and repaired in German harbours, he would need around 300 U-boats in order to have around 100 U-boats active in the area of operations near Britain.
Even after the war had started, it took a long time before the U-boats were allowed to fully exploit their devastating potential and before their rate of production was significantly raised to compensate for losses and increase their numbers; in 1943 Doenitz was promoted to head of the German Navy and submarine production was dramatically increased, but it was now too late; the German U-boats now faced much stronger British anti-submarine forces, which were equipped with new technologies, new tactics and a new commander, Admiral Max Horton, a former submarine captain and commander of the British submarine force, who knew how best to fight against other submarines, and by then merchant ships were being constructed faster than the U-boats could sink them; in May 1943 Doenitz lost 41 U-boats in 3 weeks; the U-boats were no longer just the hunters, they had become the hunted as well.
Despite this, U-boat activity expanded to the South atlantic, the US East coast, the Carribean and the Mediterranean, but the main battlefield remained in the North atlantic sea routes to Britain and there they lost the battle; until the end of 1942, the Germans sunk an average of 14 ships for each U-boats lost, but from 1943, the rate dramatically reduced and U-boat losses increased dramatically; during WWII they sank a total of 3000 allied ships, mostly merchants, and 14.5 million tons of shipping, but they also lost almost 800 U-boats, which was about 80% of all active U-boats and more than two thirds of the 1170 U-boats that were built.
The other main submarine fleets:
The Italians had built a large fleet of submarines, but their submarine tactics were not very efficient, except in the operation of underwater divers, a highly efficient method of underwater warfare which they invented and excelled in; the 'Comando Raggruppamento Subacquei e Incursori Teseo Tesei' (COMSUBIN) was the elite combat frogman force and one of the Italian special forces.
Italy was the first nation to use frogmen and human torpedoes; the Italian Naval Assault Divisions are considered to be the precursors to modern Naval Special Forces; their record can be traced back to WWI and the operation against the Austrian Hungarian Battleship Viribus Unitis in Pola Harbour in 1918; other famous operations are Trieste, Suda Bay, Alexandria, Gibraltar and Malta; With the success of this group Great Britain and Germany soon followed suit.
Italy's frogman group originated in 1938 as the 1a Flottiglia Mezzi d'Assalto (1st Flotilla Assault Vehicles), which was reformed in 1940 as the Decima Flottiglia MAS (10th Flotilla Assault Vehicles, X MAS); it is a matter of pride that Italy's Naval Special Forces pre-date both the U.S. Navy Underwater Demolition Teams, formed in 1943 and forerunners of the better-known U.S. Navy SEALs, and the British Royal Marines Special Boat Service formed as an offshoot of the Special Air Service in 1941.
The Japanese had built a large fleet of remarkable submarines, but misused them; they used their submarines mostly in cooperation with surface warship convoys and mostly against enemy warships, which are much harder targets than merchant ships; as a result, their submarine achievements were low.
British submarines were a secondary force in the Royal Navy and they mainly attacked Axis warships, including the sinking of 39 German U-boats, and participated in many intelligence operations, but their main strategic contribution was made by a small force of smaller coastal submarines which operated from the heavily attacked tiny island of Malta in the center of the Mediterranean Sea; this small force kept sinking the Italian supply ships which provided fuel and other equipment to the German Italian forces which fought in North Africa and the increasing shortages this caused limited the abilities of the Axis forces and eventually led to their defeat.
After the attack on Pearl Harbor, which destroyed a large part of the US surface Navy, they US was left with two two main naval forces, the few remaining aircraft carriers and the submarine fleet and whilst the aircraft carriers were given the task of destroying the Japanese Navy, especially the Japanese carriers, the main task of the US submarines, just like the German U-boats, was to suffocate Japan's military industry, cut off its oil supply, starve it and prevent mass troop movements by sea, all of which was done by sinking the Japanese merchant fleet on which it was so dependent as a nation of islands.
Initially US submarines suffered severely from faulty torpedoes and other problems, but when these problems were ironed out in mid 1943, the US Pacific submarine force had tremendous success, efficiently sinking Japanese shipping and also with secondary tasks such as rescuing downed airmen; the US submarines sank almost 1300 Japanese merchant ships as well as many warships, whilst only losing 52 submarines out of a total of 288; this remarkable achievement was aided by the fact that unlike the British, the Japanese neglected to properly escort and protect their merchant ships until the end of the war.
The Russians started the war with 58 submarines in service and the main class was the Bars; the Germans regularly faced this effective Soviet submarine fleet; 24 Russin submarines were lost during the war.