Simplifying units interactions of Transports, Submarines, Destroyers & planes


  • You might run out of paper.  :-D


  • You might run out of paper.

    :-D…LOL…No it’s ok. I work at home and have some extra paper…But now the printer suffer a first shot attack!!!


  • What no destroyer in your driveway ? Shame on you !  :lol:

  • '17 '16

    @crusaderiv:

    You might run out of paper.

    :-D…LOL…No it’s ok. I work at home and have some extra paper…
    But now the printer suffer a first shot attack!!!

    :-D :-D :-D

    It is a very very very long post.
    I know it is confusing, his house rules are inside historical and game comments.
    I tried to bold some points but it is almost as it is on the website.
    Sorry.


  • I agree that the OOB rules are at best overly simplistic and at worst inaccurate in depicting the way submarines in WWII interacted with surface ships and aircraft.  A game rule set which tried to model the full variety and complexity of these historical interactions would be hopelessly complicated and impractical.

    I do, however, want to comment about a couple of elements in Justin Royek’s long post (reproduced by Baron Munchhausen).  One has to do with the assumption (expressed, for example, in the sentence “Sonar did not always detect a submarine because the submarine’s were [remaining silent?]”) that subs could evade sonar detection simply by not making any noise.  This actually applies only to one sonar detection technique: passive sonar, which involves using hydrophones to listen for sub noises.  It has no effect on the other sonar detection technique: active sonar, which involves sending high-frequency sounds pulses (“pings”) into the water and then listening for an echo as a pulse bounces off a sub’s hull and gets reflected back to the destroyer.  Active sonar could, of course, be fooled to some degree by various techniques: sitting on the bottom (in shallow waters), hiding under a temperature or salinity inversion layer in the water, or staying on the surface (at night).  But the point is that simply staying silent does not in itself make a sub undetectable to sonar.

    The other element has to do with this paragraph:

    “Destroyers were not designed to defend against enemy submarines, they were designed mostly as fleet escort ships or to hunt down enemy torpedo boats. The name destroyer comes from the designation of the ship’s role as a torpedo-boat destroyer. Destroyers were usually not designed to take on subs. However a new class of ship was called a destroyer escort or DE as it was known. These were ships designed to take on enemy submarines.”

    It’s true that destroyers were not originally designed as ASW platforms.  As Justin Royek notes, “torpedo-boat destroyers” originated as ships intended to protect larger vessels against attacks by torpedo boats.  As destroyers evolved, however, it was discovered that they were extremely versatile (and comparatively cheap) high-speed ships which could perform a variety of useful functions in support of other vessels (“maids of all work”).  One function, ironically, was to supersede torpedo boats as surface-attack torpedo launchers.  Another function was anti-submarine warfare.  Destroyers proved very good in this role because (unlike larger ships like cruisers and destroyers) they were very fast and agile.  Smaller ships that were good at ASW, like corvettes and frigates (the latter also called destroyer escorts), had comparable agility to destroyers, and were indeed specifically intended as ASW ships, but they were somewhat less capable in that role than destroyers because they were slower (and in the case of corvettes, which had single screws, a lot slower).  Destroyers also had the advantage of being much bigger than corvettes, so they were more livable for their crews on extended missions, more stable in rough water, and could carry a greater load of depth charges.  Frigates / destroyer escorts, which were also sometimes called “twin-screw corvettes”, filled a niche roughly in between the covette and the fully-fledged destroyer, though perhaps a bit closer to the destroyer side than to the corvette side.

    Anyway, with regard to A&A, it’s certainly true that the rules don’t reflect WWII submarine warfare and ASW in a detailed and accurate way – but on the other hand, it’s perfectly reasonable for the rules to depict destroyers as having ASW abilities.  One can argue about what the specific details of how those capablities should be expressed as combat values, but the capabilities themselves have a real historical basis.


  • What no destroyer in your driveway ?
    Shame on you !

    No destroyer but I have something better… She Wolf of the SS in my bed room… 8-)


  • @crusaderiv:

    No destroyer but I have something better… She Wolf of the SS in my bed room… 8-)

    Do you mean the lady herself or just the DVD of the movie?


  • The idea that subs have cannot go through a sea zone inhabited by a hostile destroyer goes against the historical realities of naval submarine warfare. Submarines were often able to sneak in undetected. A submarine can choose whether or not to do combat in a sea zone with a hostile destroyer.
    Totally agree…

    I am going to make it so that a submarine’s first shot strike is not negated by a destroyer and submarines can transit through sea zones inhabited by enemy destroyers to another hostile sea zone. When doing this, a submarine does not have to stop and conduct combat with a hostile destroyer in a hostile sea zone.
    Correct…

    If a sub goes through a sea zone with a destroyer, just like an air unit goes through a hostile territory with an AA gun in it, a destroyer will roll a die roll for the destroyer. The die roll is a standard “2” or less for a standard destroyer’s die roll. This is to simulate destroyer attacks on subs.
    Sorry it’s not the same at all… silent running remember…


  • Well I mostly agree with the comments and idea.

    • I love the idea about the carrier aircraft defend after a first shot attack and I think I will add it.

    I already used most of the rules enumerated in the text.
    But I would like to change some like this one: Destroyer always take the first hit after a sub first shot attack.
    I think the Attacker Sub must choose is target and the principal target was: cargo, transport carrier and Battleship.

    One think is sure, I’ll keep my the sonar and anti sub patrol rules.
    (Plane and destroyer must find the sub before to attack, 2 or less).
    And I think is the best way…

    Also, I don’t have doubt that some sub shoot planes but which was the percentage of efficiency?
    Sub defend at 1 against airplane…is it fair?

    AL


  • The lady herself of course… :-P

  • '17 '16

    @Baron:

    However, maybe the 1:1 rule can be kept if playing with plain Classic Transport.
    That way, it becomes the defender decision to choose a transport unable to defend @1 because it is taken as casualties instead of a Destroyer.
    This would let the Destroyer his reaction roll @2 against Sub while transports are used as fodder.

    This can become a way to see some Submarines destroying transports while being sunk by Destroyers defense.
    This can figure somehow and provide the feel of an Atlantic battle in a game where there is no merchant’s convoy like 1942.2
    .
    Some subs surprise the defender convoy but usually attacking the less defended and slower unit in it.

    @CWO:

    WWII battleships were not slow, especially the modern ones of 1930s and 1940s vintage. The “slowest” modern battleships had a maximum speed of about 27 knots, and the fastest ones of all, the Iowa class, could do better than 33 knots, which on par with what a typical true destroyer could do and better than a destroyer escort could do. As a rough generalization, you could say that the WWII battleships which dated from the WWI era weren’t fast enough to keep up with carrier task forces, and hence tended to be used for shore-bombardment and convoy-escort duties, so there would be some justification in giving them special treatment regarding speed…but in terms of A&A naval units, the only ones that would realistically (based on real-life average performance in WWII) be too slow to retreat would be naval transports.

    In fact, Destroyers defending against Submarine attacking and sinking transports have totally disappear and can no more happen with the OOB Taken Last rule for Transport.
    This documentary provides interesting infos on US Submarines working in the Pacific Theatre of Operation.
    It shows how it was a seldom occasion to sink a surface warship because of their speed.
    The main explanation starts around 32 minutes to 36 minutes. Especially 32m.30s to 33 m.
    SUBMARINE WARFARE OF WORLD WAR II - Military History (documentary)
    https://www.youtube.com/watch?v=QzZYDa_nA0w

    Hi CWO Marc,
    I have the impression that submarines’ targets were rarely Destroyers. That most of the time, it wasn’t warships but merchants ships. And when attacking warships, it was mainly Carriers, Battleships and Cruisers.
    Destroyers were too fast, maneuverable, and too well equiped to try to sink them.
    Am I wrong?

    If I’m right, then it seems not very historical and inaccurate to let subs sink Destroyers instead of troop transport ships.
    So the Taken last rule is less interesting from the sub warfare tactics POV while, from surface vessel POV, it was certainly strange to use transports as cannon fodders for costlier surface warships, such as Carrier and Battleship.

    Also, thanks for your additional historical comments on Justin Royek assumptions.


  • I have the impression that submarines’ target were rarely Destroyers. That most of the time, it wasn’t warships but merchants ships. And when attacking warships, it was mainly Carriers, Battleships and Cruisers.
    Destroyers were too fast, maneuverable, and too well equiped to try to sink them.
    Am I wrong?

    You’re not wrong….that’s why I mentioned that destroyer and/or escort must be the last target for a sub but if sub can choose is target…is it too strong?

    AL

  • '17 '16

    @crusaderiv:

    Well I mostly agree with the comments and idea.

    • I love the idea about the carrier aircraft defend after a first shot attack and I think I will add it.

    I already used most of the rules enumerated in the text.
    But I would like to change some like this one: Destroyer always take the first hit after a sub first shot attack.
    I think the Attacker Sub must choose is target and the principal target was: cargo, transport carrier and Battleship.

    One think is sure, I’ll keep my the sonar and anti sub patrol rules.
    (Plane and destroyer must find the sub before to attack, 2 or less).
    And I think is the best way…

    Also, I don’t have doubt that some sub shoot planes but which was the percentage of efficiency?
    Sub defend at 1 against airplane…is it fair?
    AL

    This could be another way of playing Subs on defense being attacked by DDs and planes, allowing Subs a little capacity of destroying planes with their @1 roll if there is no more warships available to take the hit.

    The issue will be that Sub on offence would have two attack values, @2 against warships and @1 against aircrafts and it couldn’t be roll simultanuously.


  • @Baron:

    I have the impression that submarines’ targets were rarely Destroyers. That most of the time, it wasn’t warships but merchants ships. And when attacking warships, it was mainly Carriers, Battleships and Cruisers. Destroyers were too fast, maneuverable, and too well equiped to try to sink them. Am I wrong?

    In the Battle of the Atlantic, the primary job of German submarines was to sink merchant ships.  This made good strategic sense.  Britain imported all of her oil, many of her raw materials and much of her food, so if those supplies could be cut off (or greatly reduced), Britain would be starved into surrender.  This made the merchant ships much more valuable U-boat targets than warships.  Think of it this way:

    • If U-boats had (for the sake of argument) sunk all of Britain’s warships but none of Britain’s merchant ships, Britain would have continued to survive (and continued to fight its air war against Germany).

    • If U-boats had (for the sake of argument) sunk all of Britain’s merchant ships but none of Britain’s warships, Britain would have starved and would have run out of fuel, at which point all of its warships would have been put out of action because of empty oil tanks (or would have been compelled to go elsewhere for fuel, like Canada or the US, which would basically have made it very awkward for them to operate in British home waters).

    So that’s why the U-boats prioritized targeting merchantmen.  On the other side of the battle, the job of the Allied convoy escort ships (and convoy-protection aircraft, when flying range allowed it) was to protect the merchantmen.  In that sense, both the U-boats and the Allied combat vessels and aircraft regarded the merchant vessels as “the prize” (to put it crudely) for which both sides were fighting.  For U-boats, sinking a warship was a nice bonus, but it wasn’t their primary objective.

    In the early days of the war, the Royal Navy and the Royal Canadian Navy misunderstood to some extent what their primary mission was.  At first, they placed too much emphasis on sinking U-boats.  Only later did they realize that their key objective was “the safe and timely arrival” of the convoys.  In other words, they realized that a (hypothetical) situation in which every convoyed ship arrived safely but no U-boats were sunk would be a huge success for the Allies, while a (hypothetical) situation in which great numbers of U-boats were sunk but every convoyed ship was lost would be a massive disaster for the Allies.

    This explains why long-range aircraft like the Liberator had such a huge impact on the Battle of the Atlantic.  The Allies realized that these planes could greatly increase the safety of convoys even without sinking any U-boats.  Why?  Because U-boats feared aircraft more than anything else (they had weak anti-aircraft batteries, and their deck guns and torpedoes were useless against planes), so when a plane appeared overhead they usually pulled the plug and crash-dived.  And that was the Achilles’ heel of WWII diesel-electric submarines: they were fast and long-ranged on the surface, but spending time under water slowed them down (for hydrodynamic reasons) and also ate into their operating range because diesel fuel would have to be wasted on recharging the batteries after they surfaced.  Also, submerged U-boats had a harder time torpedoing convoys than surfaced U-boats, in part because their slow submerged speed gave them just a small window of time to line themselves up for a torpedo shot before a convoy slipped away.  So to a large degree, the Allied air strategy was to try to drive the U-boats underwater as often as possible and keep them there for as long as possible.

    Don’t get me wrong: the Allies were always happy to sink U-boats, and some aircraft (like the Liberator, when it was equiped with the Leigh Light and when suitable tactics for its use were perfected) proved quite adept at killing subs.  But the Allies did their best (not always successfully) to keep firmly in mind that sub-killing was only a means to an end, not an end in itself, and that the job of “getting the convoys through” did not inherently require sub-killing.

    In the Pacific, we have an interesting variation of what happened in the Atlantic.  The American subs, by and large, concentrated on sinking Japanese merchant ships for precisely the same reason as the Germans tried to sink British ones: to strangle Japan.  Japan in WWII was strikingly similar to Britian, in the sense that both countries were resource-poor, highly-populated, industrialized islands located very close to a large continent – so it’s hardly suprising that both countries were major naval powers, since their survival depended on their merchant fleets.

    Japan, unlike the Americans, focused its Navy’s attention far too much on sinking enemy ships.  Its subs spent too much time hunting American warships and not enough time attacking the American supply ships that kept the US Navy operating thousands of miles from Hawaii.  Japanese destroyers spent too much time in warship combat and not enough time on the boring but essential job of protecting Japanese merchant ships from US submarines.  It’s a very curious blind spot that the Japanese had about the value of merchant vessels (their own and those of the enemy), possibly because their warrior culture at the time made them feel that the proper job of a warship was to fight another warship, not to look after the interests of Japan’s gross domestic product.

    The American subs in the Pacific, incidentally, were never shy about taking a shot at a Japanese warship when a target of opportunity came along – just look at what happened to the Shinano.  They just kept in mind that sinking merchant ships was a potentially war-winning task, and they carried it out so successfully that, by 1945, Japan was nearing the economic bottom of the barrel and US subs were starting to run out of targets.

  • '17 '16

    Thanks for this develop answered post Marc.

    I think many threads on Submarines warfare should get link to your explanation on the strategical meaning of subwarfare.
    I would add that it is very helpful the way you provide a wide scope and a comparison on the two theatres of war.

    I will probably add your answer somehow within some of my existing post on sub warfare historical background.

    I still have one question:
    does a Sub on hunting warships missions, such as the IJN Subs you talked about, can be able to attack and sunk a destroyer?
    Or a they too big fishs to fry for Subs?
    And does such a feat was only possible in very special circumstances?
    Example: such as dark night, sub having the surprise effect and DD traveling at half speed.

    Or is it that, when a Sub have a Destroyer up on the cross-wire, their was always bigger and easier target, since DDs are escorting other warships?
    This would explain why there is so few record of a Submarine sinking a Destroyer.

    Below is a start I found on this specific matter:

    QUESTION: I have a question submarines vs destroyers naval combat who will win?

    As a Submariner I can tell you we fear no vessel, but love to hunt them!

    Submarines have a massive advantage in that they can see or hear the Destroyer well before the Destroyer would ever be able to find it. This allows the submarine the ability to fight on its terms.

    Back in WWI & WWII Submarine engagement range was a max a 2-3 thousand yards, but typically 1-2 thousand (less than 1 mile). When the sub is at PD at these ranges, the scope could be seen, and Subs submerged where very slow (3-6 kts). If a destroyer spotted the scope they could quickly get to that area (>30kts) and commence depth charging the Sub. It would take a Destroyer at 30 knots only 2 minutes to be on top of a submarine at 2,000 yards. A submarine at 6 kts would only beable to move 400 yards at most by this time. But if it is 1000 yards and 3 knots the Destroyer would be on them in 1 minute and only travel 100 yards. This helped the destroyer get ordinance on top of the sub quickly due to short range encounters.

    Today a modern Submarine can attack from much much longer ranges, and are very fast when submerged. Using the idea from above is not the game of today, and that is why WE fear no vessel, not even a tin can destroyer. The Submarine can attack from several miles with much better sensors, and weapons, and can quickly clear the area before the destoyer (or any other target) has a chance to pounce.

    You can’t kill what you can’t see

    https://answers.yahoo.com/question/index?qid=20091126181349AAok1Rr

    QUESTION: Has anyone heard of submarines during WW1/WW2 using offensive tactics as a means of defence against destroyers? I vaguely remember a report of a submarine firing a torpedo directly at a closing destroyer head on. Since depth charges had limited range, and shells would just ricochet of the top of the water, it would seem that a partly submerged submarine at periscope depth would have the first shot. Failing this it would seem relatively straightforward to design the submarine to release some mines across the destroyers path as it retreats away under battery power. Perhaps I am missing something obvious here but surely this sort of tactic may have rendered escorts redundant at a stroke?

    As far as I know the direct attack was the only means available to a destroyer in the first half of the 20th Century.

    The basic destroyer attack procedure was to point the ship at the target and head towards it at a moderate speed. Once the ship was generally within 1,000 yards, sufficient sonar data regarding the submarine’s heading and speed should have been determined. At that point, the destroyer’s helm would maneuver on a “collision course” with the target. Adjustments would be made in the DD’s course to account for the approximate depth of the sub, calculating the amount of time it would take for a depth charge to sink to the lethal level. Depth charges dropped from the stern tracks would be in evenly spaced intervals. The port and starboard throwers would send DC’s approximately 50 yards out on either side - forming an elongated diamond shaped pattern. The goal was to pass just far enough ahead of the submerged target and launch the DC’s in the hopes that the submarine’s travel would take them right into the path of the sinking ordnance.


    I believe there is a basic misunderstanding in this topic. Anti Destroyer warfare for the submarine was basically avoidance. To stay hidden. The firing of a torpedo was usually the first indication that a submarine was close.

    Submarines primary mission was to destroy high value targets. Those being supply, or oil tankers, or troop ships. Wasting a torpedo on a destroyer defeats the submarines mission. The destroyer wins in that scenario. Remember the mark of sucess for submarines was in the tonnage of ships they sank.

    Submarines had a limited amount of weapons and would have to withdraw when these were expended.

    Destroyers lose the battle when they are not able to protect the ships under their support.

    Anti-submarine doctrine actually directs destroyers to maneuver to take a hit from a torpedo rather than allow it to hit a higher value target. The Captain of my ship was less than enthused about this directive. Submariners new this and could set the run depth of their torpedoes to pass under a destroyer and continue to its target.

    Simple example: Destroyer’s draft less than 20ft. Supply ships draft more than 20ft.

    Run depth of a torpedo was always a consideration for submariners. To shallow and wave action could effect its ability’s to run straight. Set to deep and it could pass under its intended target. Remember WWI and WWII torpedoes were mostly contact weapons and not guided.

    Submarines always have an advantage over destroyers as they can hear a destroyer’s active “pinging” at at least twice the range that it would take the destroyer to get a return from it’s signal. All surface ships make considerably more noise than a submarine running submerged. Avoidance was easy.

    I was a destroyer sonarman for 6 years during the early 1970’s.

    http://www.military-quotes.com/forum/anti-destroyer-tactics-t68566.html

  • '17 '16

    I finally found something interesting about Submarine sinking Destroyers:

    USS Albacore (SS 218)

    The Navy’s first vessel named Albacore was a slow scout patrol boat loaned to the Navy in July 1917 for patrol service during World War I. She was returned to her owner in January of 1919. The keel for the second Albacore, SS-218, was laid April 21, 1941 at the Electric Boat Company of Groton, CT. Launched on February 17, 1942, she was commissioned on June 1, 1942. Albacore’s war operations spanned the period between 28 August 1942 and December of 1944 during which time she completed ten war patrols.

    She was credited with sinking eight Japanese ships including an aircraft carrier, a light cruiser and two destroyers. Her loss during her eleventh patrol on 7 November 1944 was witnessed by a Japanese patrol craft. Albacore earned the Presidential Unit Citation, nine battle stars and other awards.

    http://www.ussalbacore.org/html/albacore_story.html

    Between 7 June and 9 June, Nautilus replenished at Midway Island and then resumed her patrol to the west. By 20 June, she was operating off Honshū at the northern end of the Tokyo-Marshall Islands supply route. On 22 June, she damaged a destroyer guarding the entrance to the Sagami Sea off Ōshima. Three days later, she sank the destroyer Yamakaze and damaged an oil tanker. On 27 June, she sent a sampan to the bottom and on 28 June, after damaging a merchantman, underwent her severest depth charging, which forced her back to Pearl Harbor for repairs, 11 July to 7 August.

    http://en.wikipedia.org/wiki/USS_Nautilus_(SS-168)

    USS Reuben James (DD-245)

    On 31 October 1941, the Reuben James was one of five destroyers escorting convoy HX-156, close to the coast of Iceland, about 600 nmi (1,100 km; 690 mi) west of the island. The James had just begun turning to investigate a strong direction-finder bearing when a torpedo fired from U-552 struck her port side and caused an explosion in her forward magazine.
    The entire bow section of the destroyer was blown off as far back as the fourth funnel and sank immediately. The stern remained afloat for around five minutes before sinking; unsecured depth charges compounded the damage, exploding as they sank and killing survivors in the water. One hundred and fifteen of her 160-man crew were killed, including all the officers.

    The destroyer was the first US Navy warship to be sunk in World War II.

    http://en.wikipedia.org/wiki/German_submarine_U-552


  • Well write Marc but merchant marine was not only the target.
    Don’t forget that U-Boat had mission. And sometimes it was clearly to sink warship. (Remember Scapa flow).
    The mission of the Japanese sub was to sink US warships. (Without great succes)
    So I think the sub must choose is target and the last must be the destroyer.

    AL.


  • @crusaderiv:

    Well write Marc but merchant marine was not only the target.
    Don’t forget that U-Boat had mission. And sometimes it was clearly to sink warship. (Remember Scapa flow).
    The mission of the Japanese sub was to sink US warships. (Without great succes)
    So I think the sub must choose is target and the last must be the destroyer.

    I never said that merchant ships were the only targets of submarines in WWII.  I said they were the primary targets of submarines, because they were the targets that had the highest value from a strategic point of view.


  • @Baron:

    I still have one question:
    does a Sub on hunting warships missions, such as the IJN Subs you talked about, can be able to attack and sunk a destroyer?
    Or a they too big fishs to fry for Subs?
    And does such a feat was only possible in very special circumstances?
    Example: such as dark night, sub having the surprise effect and DD traveling at half speed.

    Or is it that, when a Sub have a Destroyer up on the cross-wire, their was always bigger and easier target, since DDs are escorting other warships?
    This would explain why there is so few record of a Submarine sinking a Destroyer.

    The different variables you list in your question pretty much summarize the answer, which is “It depends.”  A destroyer is, in some respects, like any other surface ship: it floats because its hull displaces enough water to compensate for its weight, and it can be made to sink if you increase its weight (by filling it up with water) to the point where the water it displaces isn’t enough to hold it up.  So in that sense, there’s nothing magical about a destroyer.  As with any other ship, the best way to fill it up with water is to blow a hole in its hull below the waterline, using such weapons as torpedoes, mines or explosive shells.  Torpedoes are arguably the most practical and versatile way of blowing a hole in a ship’s hull below the waterline, so let’s focus just on torpedoes for the sake of brevity.  Let’s also just focus on submarine-fired torpedoes, since this is what the present rule discussion is about, even though torpedoes can also be delivered by surface ships and by aircraft.

    So the two questions to consider become the following: to what extent is a destroyer more likely (or less likely) than any other ship to have a submarine put a torpedo into its side, and to what extent is a destroyer more likely (or less likely) than any other ship to sink if it’s been torpedoed?

    Let’s take the second question first because the answer is fairly straightforward.  Basically, I’d say that a WWII destroyer is more likely to sink from a torpedo hit than a WWII cruiser or a WWII battleship because destroyers were pretty fragile, as their nickname “tin can” conveys.  They were basically the floating equivalent of a Zero fighter: fast and agile, but completely lacking in armour.  Cruisers and battleships were armoured (to various extents) along their waterlines, and battleships typically had sophisticated anti-torpedo features such as liquid-loaded bulges designed to absorb and dissipate torpedo blast effects.  On the other hand, a WWII destroyer was probably less likely to sink from a torpedo hit than a merchant vessel.  Destroyers are combat vessels, so they’re designed with more watertight compartmentalization than civilian merchantmen, which helps to keep the ship afloat if it’s been torpedoed.  Also, destroyers are manned by naval personnel, not merchant mariners, so this theoretically (but not invariably) means a higher standard of discipline and training, which can make the difference between life or death in a damage-control situation.

    Now for the first question, which breaks down into two components: how likely is a sub to be taking a shot at a destroyer, and how likely is the sub to actually hit its target?  To get back to my basic answer: it depends.  Is the sub operating in the deep ocean?  If so, it’s more likely to run into a convoy than a naval force because the convoys were more numerous.  Is it operating near a commercial port?  Again, the chances are that it’ll run into a convoy rather than a naval force.  Is it operating near an enemy naval base?  Here, the chances rise that it will spot a warship.

    If the sub runs into a convoy, what will it choose to attack: the merchantmen or the escorts?  The merchantmen were supposed to be the priority targets, so in principle a sub captain who has a target choice will, all other things being equal, attack the merchant ship rather than the escort vessel (unless he’s following Japanese naval doctrine).  If things aren’t equal, the answer might vary.  For instance, a U-boat captain who’s given a choice between a fast cargo vessel and a destroyer lying motionless in the water (let’s say, due to engine trouble or because it’s picking up survivors) might take a shot at the destroyer because it’s an easier target under those circumstances.  Another variable is a U-boat is at the end of its mission and low on torpedoes, in which case the skipper might be more choosy about what to attack.

    Target speed, target size, target distance, target orientation and target course are hugely important variables.  WWII destroyers were at the high end of the surface-ship speed scale, so this made them harder to hit than slower ships…assuming they were operating at their maximum (flank speed) at the time a sub ran into them, which they probably rarely were because most warships (for fuel economy reasons) tend to operate at a slower cruising speed much of the time.  WWII destroyers were near the low end of the size scale (though frigates and corvettes were smaller), so this made them harder targets than cruisers and destroyers.  Distance and orientation are uncontrlable variables, since they come down to luck: a nearby destroyer lying perpendicular to a sub will obviously be an easier target than a distant aircraft carrier lying bow-on.  Course is another big variable: a zigzaging ship is harder to hit than one traveling on a straight course, and a torpedo shot will be affected depending on whether the surface ship is headed toward the sub, away from it, or sideways across its track.  Another variable: does the ship have lookouts who are on their toes (ready to spot incoming torpedoes promptly) and a sharp captain who will promptly turn his bow towards the torpedo to comb its track?  If so, the odds of a hit are greatly reduced.  Agile destroyers can obviously perform such maneuvers better than a tubby cargo vessel, so that’s a point in their favour.

    So the upshot of all this is that there’s no single answer to the question of why destroyers were (or weren’t) sunk to a greater and lesser degree than other ship types.  In a very general sense, the main factors at play were probably: a) that subs didn’t often take shots at destroyers since they were less important strategically than merchant ships; b) that destroyers tended to be hard targets to hit due to their speed and agility; and c) that successful torpedo hits on destroyers could very well sink or severely damage them, due to their relative fragility.

  • '17 '16

    Thanks again for taking time to make such an elaborate post.
    I really appreciate.
    Baron

    I wanted to integrate also this post on Sub of yours in this thread:
    @CWO:

    I’ve just revised the list of IJN Submarines to find if there is many of them which were sink by planes. It appears that there is not much. Most of them were sunk by destroyers or submarines.<<

    And there’s a good reason for this. Japanese subs in the Pacific and German subs in the Atlantic played almost completely different roles. The Japanese considered that the primary mission of a sub was to sink enemy warships, and IJN subs therefore wasted a lot of time trying to do so rather than attacking the USN’s supporting transport ships (which, being slower than warships, would have made much easier targets). The USN therefore didn’t have to devote a huge effort to ASW in the Pacific.

    In the Atlantic, Germany considered the primary mission of a sub was to sink enemy transport ships. The cargos being convoyed by these ships were vital to the Alllied war effort, so the Allies placed more and more priority on defending them as the war went on. In other words, German subs were a high-priority target for the Allies, whereas Japanese subs were not. A related factor was that the Atlantic is only about half the size of the Pacific, and that the Allied convoys sailed on fairly well-defined routes, so these elements made combat encounters with subs much more likely in the Atlantic than in the Pacific.

    The Americans, interestingly, used their own subs in the Pacific much as the Germans did in their Atlantic: the USN’s submarines concentrated on attacking the Japanese shipping routes bringing oil and other critical supplies to the Japanese home islands. USN subs might have suffered considerable casualties in the process if the Japanese had taken this threat seriously, but Japan – despite being a maritime nation – gave astonishingly little importance to convoying their merchant ships and to developing their ASW capabilities.

    So in a nutshell, Japan had a faulty understanding of how Japanese submarines should be used for maximum effect against the Americans, and a faulty understanding of how effectively the Americans were using their own submarines against Japan.

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