Think about the problem U-Boats were meant to solve: Britain and her European allies were heavily reliant on their colonies and the United States for resources and war materiel. U-Boats were ruthlessly efficient at seeking out and sinking those merchant convoys.
The Americans *did* build a submarine fleet, which they deployed to great effect against Japanese merchant convoys in the Pacific. But because the German war machine was supplied by mines and factories in Europe, there wasn’t much need for widespread deployment of submarines by the Allies in the European theater.
The US and her allies did have subs, but they were 1) not as big a source of news as the Uboats, hence they didn’t leave a huge mark in the cultural consciousness of the former Allies, and 2) the the foremost use of submarines by the allies was in the Pacific where within 3 years the US virtually sank the entire Japanese merchant marine.
Two of the most decorated USN ships of WWII were submarines. U.S.S. Thresher, and U.S.S. Narwhal who both were awarded 15 battlestars for the war.
Japan never devised a coherent convoy system. Basically 1 admiral was in charge of defending the entire Japanese Merchant fleet and the resources he was given were just a few corvettes and destroyers. Japanese crews didn’t train much in anti-sub warfare either and the Japanese airforce didn’t really devise the use of air power for anti-sub tactics.
American submarines were turkey shooting Japanese shipping from the moment the US entered the war. They basically did everything the Uboats tried to do, except Japan kept putting off the idea of doing anything about it until it was too late.
By the end of the war US subs were sailing into the inner sea of Japan and the Japanese battleship-turned-carrier Shinano was sunk by a submarine in Japanese home waters.
A world war two submarine fighting against another wwii submarine would be similar to a two blind men fighting each other in a 1000 yard space. They can yell (sonar) and listen (hydrophone), throw stones at a random locations (torpedoes) but at the end it is almost impossible to cause any harm to each other.
The United States had many technologies beyond depth charges and the hedgehog that were highly effective at killing UBoats. In fact, aircraft and aircraft deployed assets including sonobuoys and homing torpedoes did extremely well.
Check this out:
[https://www.youtube.com/watch?v=Y2bA-4eNG7o](https://www.youtube.com/watch?v=Y2bA-4eNG7o)
[https://www.youtube.com/watch?v=IDvHT9MncW4](https://www.youtube.com/watch?v=IDvHT9MncW4)
During WW2, submarine-submarine technology and tactics was in its infancy/didn’t exist. Sonar was primitive, anti-submarine homing torpedoes barely existed, and the submarines themselves were slow and had poor underwater endurance. The technology just wasn’t there.
Likewise, the need also wasn’t there. By the point in the war in which ASW-submarines became at all viable(even in theory), the uboat threat was essentially over and conventional ASW tactics and weapons were more than sufficient
The purpose of a submarine is not to counter other submarines. Submarines, especially in WW2, were used to utilize their ability to get behind enemy lines to harass shipping. They used their periscope to see targets and would engage with targets using their deck gun and torpedoes.
Destroyers and aircraft were purpose built to locate and attack submarines. Aircraft allow you to scan a large swath of the ocean quickly and surface ships can have larger radar equipment and plenty of ordnance for neutralizing a submarine. I believe most submarine attacks happened in the middle of the passage where planes didn’t have the range to cover the convoy. And still to this day, air aircraft like the P-8 Poseidon and helicopters on anti-submarine warships are used to locate and destroy submarines.
By far the most effective weapon against the U-boats was the convoy system.
U-boats were slow on the surface and almost immobile once they dived. The odds of catching ships go way up if you get many chances. Convoy put all the ships in one location, so if the U-boat missed the convoy there would just be empty ocean to patrol.
Meanwhile, the U-boats were difficult to hunt except when they were attacking ships. Because the convoys were escorted by ships capable of attacking U-boats, that meant that any time a U-boat was ready to attack a ship (and thereby expose itself to counterattack) there were warships RIGHT THERE to pounce.
Aircraft were also extremely dangerous to U-boats, which until the very end of the war had to surface to recharge batteries or move any significant distance. Long-range patrol bombers equipped with radar and spotlights (the famous Leigh light) would swoop in and illuminate them before they could react, and drop bombs and depth charges. Even when they didn’t destroy U-boats, aircraft could force them to submerge and prevent them from moving while the convoy moved away.
Prior to guided torpedoes submarines were very limited on how they could engage other submarines. They could fight with the deck gun but that would be a waste of time. It’s much better to handle the anti submarine role to fast destroyers, which can carry more depth charges + other armaments and generally be used in more roles.
If we compare a WWII era submarine to a WWII era destroyer, the sub is worse than the destroyer in every single way except for the fact that it can go underwater for a bit. The destroyer is cheaper, faster and better armed. If they find the sub, they have a massive advantage.
If you try to use a submarine to fight against your opponent’s submarines, you aren’t any better at finding it than the destroyers are, and once you do find it, you don’t have the destroyer’s weapon plus speed advantages.
That being said, bombers were the weapon that really turned the tide against subs. Bombers are much much cheaper and faster than either ship. Bomber patrols would fly around until they spotted a sub then attack. After both sides spot each other, a B-24 could usually close the distance in about the same amount of time that it took a U-boat to close all their hatches and dive. Ideally, right as the ship is slipping under the water, the plane is crossing overhead dropping depth bombs on it.
The Americans did use unrestricted submarine warfare in ww2 (on Japan), and the UK and other allied countries did have submarine fleets.
But submarines are slow and not very good at sinking things. They are also quite vulnerable to aircraft. At least in ww1 and ww2.
The allies had capital ships that mostly controlled the Atlantic and Mediterranean, and so the axis basically didn’t have any shipping to sink except from Norway to Germany and from Italy to Libya, and Vichy France to French Algeria. So the central powers and axis powers didn’t move huge amounts of cargo unless they could escort it with capital ships because the allies would have obliterated it very easily.
The Mediterranean and Norwegian coast mostly have solid air cover, so aren’t hugely suited to submarine warfare for the allies.
Japan on the other hand never seemed to regard the security of their cargo ships as worth doing much about. Which both at the time to the allies and in hindsight makes no sense. The japanese would have solo unescorted ships running resources from what is today Vietnam, Indonesia, Malaysia etc, back to Japan. And the Americans basically started hunting them ruthlessly. Now the logic here might have been oil, and fleet concentration. Dividing up their fleet to spend oil to escort convoys might have been something they didn’t think they could risk, or they just didn’t take the threat seriously until it was too late. After all a submarine from Australia, Sri lanka/India or Hawaii had a long way to go and so they might not have thought the Americans had enough subs to worry about. They were wrong.
The military supply convoys were escorted by the Japanese and were not hugely vulnerable to submarines. But cargo, pows.. Not so lucky.
In terms of anti submarine warfare, tools like asdic (SONAR) aircraft patrols, fast surface ships with depth charges and wargames (the western approaches wrens) were ultimately what dealt with submarines.
At the start of the war most of the allies didn’t even really have effective anti submarine weapons. So the Germans had an advantage in 1939 that was least partially gone by the time the Americans joined the fray in 1941. The weapons the allies (and Japanese had) might have been good against a 1918 submarine but a 1930s one that was faster and could dive deeper, those were a challenge.
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