Das Boot and helpless subs

I was watching Das Boot, which is a movie about submarines from a German point of view. Like all movies involving subs the boat was completely helpless when being attacked by a Destroyer. Was this always true? Couldn’t the sub fire her stern torpedoes when the destroyer passed over after a depth charge run? Or something?

That would give away their position and even if they sank the destroyer the other destroyer would get them. Navy ships usually sail in groups.

To fire the torpedoes accurately with the tech available in WW1 or 2 you needed to come to periscope depth and get a visual. That’s a modest risk at night and when approaching a convoy that doesn’t know you’re there. I suspect coming to periscope depth with a destroyer that knows your rough whereabouts and is expecting you will result in you being spotted. I don’t think torpedoes are good weapons against something as fast and manoeuvrable as a destroyer anyway: particularly one that is not going to be hanging around on any given course or speed, knowing of your presence. And once you are spotted and your precise location is known, the destroyer will depth charge you goodbye.

Later in the war the Germans had acoustic homing torpedoes which were optimized for use against escorts. Got quite a few of them too, not that it stopped the bleeding of the U-boat arm. You have to be at periscope depth to fire one tho, which is dangerous when destroyers are trying to depth-charge you out of the water.

Torpedos of the day (which ran just under the the surface) were adequate for hitting an unawares merchant ship traveling a steady course, but being unguided weren’t of much use against an armored opponent who can maneuver rapidly. Furthermore, subs of the day were much slower than a surface ship when submerged, and basically totally vulnerable (having essentially no armor) when on the surface. (Plus, the hull shape of U-boats made for less than ideal handling on surface; modern round-hull subs are even worse in rough seas.) Submarines scored some exceptional victories, most famously the HMS Ark Royal, the HMS Courageous, and the USS Block Island, but they did so by stealthy approach, quick tactical maneuvering, and at great risk to the hunter.

Germany and the US both developed homing torpedos late in the war (using passive accoustic detection) and magnetic proximity detecting torps, but these were often as dangerous to the firing sub as to the target; in fact, torpedos in general are very dangerous, and the loss of at least two Cold War era US Navy subs are likely lost to torpedo malfunction; no doubt failure rates were even higher with WWII era fish. Depth charges were rarely effective by themselves–they had to get within about a hundred feet or less to make a direct kill, and in the murky North Atlantic actually making any accurate prediction of where a sub might be was pure luck–but they were very useful as harassment to force a sub commander to panic and do something really stupid, like dive too deep, attempt a speed run out of the pattern area, or run aground. Vying directly against an attacker would be playing a game of chance with bad odds; a sub would have to be lucky enough for the ship to turn its after aspect toward it to get a stern shot–it would never be able to maneuver into position fast enough to make a solution if the surface ship has a notion of where it’s at. The sub also needed to be at periscope depth to make a shot, which was contrary to evasive routines, which was to dive and run, changing depth and heading to get out of the depth charge pattern.

Submarine combat versus “cans” or “boats” (surface ships and submarines, respectively) is a curious thing, a combination of constant judgment and input, and yet drawn out for scores of minutes before a solution is obtained. You don’t want to fire before you’re in optimum position, because in firing you reveal your own position, but you want to get off the first shot, and then get the hell away; it’s really a chessman’s game rather than the blowsy broadsides between surface ships. Once a sub has given away its position, it’s lost the initiative and is badly disadvantaged.

Das Boot is not only a great movie–perhaps one of the best war movies ever made–but also hailed as being the most accurate movie about submarine and WWII naval combat. The cast was made to live in the cramped interior for the bulk of the filming, and the attention to verisimilitude–both in nautical details and German naval politics–is exceptional.


That could be a fairly tough shot to make.

Allied destroyers had two means of locating a submerged submarine. Passive sonar (essentially microphones), and active sonar.

With passive sonar, lots of nearby sound pollution (like a convoy) might make the sonar useless. Own ship’s speed also interferes (via the sound of the water on the destroyers hull). IIRC, usefull only at low speeds.

Active sonar (pinging) had short range, about 2000 yards, depending on the condition of the sea. Active sonar initially had a blind spot directly beneath the destroyer.

A destroyer would line up on the subs bearing, make a charge at it. As contact fades (indicating that you were probably approaching over the target, depth charges are dropped ahead of the target. (I forget the sinking rate of dc’s.) Contact is lost as the destroyer passes over the target, and may not be regained until after the disturbance of the water settles a bit. (A second destroyer is very usefull in maintaining contact during this phase.

Depth charges do their worst damage if they explode underneath the sub. Most inexperienced destroyers tended to set their dc’s a little shallow. The IJN especially.

Hedgehog fired contact fused bombs ahead of the destroyer.

But anyway, from the subs perspective, passive sonar is the way you are keeping track of surface ships at this point. (Remember, taking a depth charge run while at periscope depth is not recommended.) This will give a good bearing, but target speed, course, and distance will be an estimate. But speed, course, and distance are crucial to setting up a torp shot.

It wont take much of an error to miss. Destroyers are 300-350 feet long, moving as much as 32+ knots (close 1/2 mile per minute, or 44 feet per second. Close to own ships length every 8 seconds). That destroyer may not be exactly broadside to the sub (shortening the targets length/profile to the sub), and may be changing course or speed erratically.

Firing a torp as the destroyer passes overhead may seem like a good idea, but that destroyer will surely change course as soon as the last dc rolls. Does he go right, or left? The destoyer may be passing over the sub from side to side, and the torp, when launched, is going to have to make a hard turn, which is possible with a torp, but complicates the shot calculations. The torp may end up going faster than him (assuming a slow setting of 30 knots for the torp), and the torp will take some time to rise to the preset depth. (Against a destroyer, I would set it to 10 feet.) I am unsure how long a torp will take to rise up to the preset depth when launched from 300+ feet down.

Even if you got a hit at close range (200 yards or less), remember that the sub itself will be nearby, and could be damaged by the same blast. (Depth charges had a warhead charge of roughly 200 lbs of torpex, while torpedoes had three times that…)

The Germans did develop acoustic homing torpedoes, but the Allies developed “noise maker” counter measures. For safety reasons, the Germans had a minimum of 400 yards before arming it. They lost two subs to their own acoustic torps.

The Uboats typically carried 22 torps (in the type IX Uboat). Both the US and German sub captains would rather stick one in an enemy merchantman or capital ship, not the hard to hit destroyers or sub chasers.

The best defence, then, is to dive deep, and hope the destroyer skipper either loses contact with you (through good luck or a temperature layer), or thinks he got you and goes away.

U-Boats were designed for one thing: stealth. Their entire working strategy was to hunt in packs, coordinating movements by means of coded radio signals. Attacks usually came at night, and the individual u-boats, once their torpedoes had been fired, submerged and scattered. And well that they should, because once its position had been identified by the convoy’s destroyer escorts, the u-boat was defenseless. Her crew certainly could not hope to outrun the defenders – on the surface, a u-boat running at maximum speed would be traveling half as fast as the destroyer. Submerged, it moved even more slowly. The Type VIIC , for example, known as the “workhorse” of the Kriegsmarine (and this is the type of u-boat portrayed in Das Boot) had a surface cruising speed of 17.7 knots, but only 7.6 knots underwater. Add to this the fact that once a sub had been detected, a host of sonar and hydrophonic gear would be sweeping the depths for any kind of sonic trace. Since even flooding the torpedo tubes prior to firing makes a detectable sound, the u-boat’s only hope for survival is to tiptoe away.

Did WWII era German subs really carry 20 torpedoes?

The more common Type IIV (like that in the movie) could carry 11-14, plus a couple externally if specially rigged. The larger Type IX and XXI’s could carry 20-24 torpedos internally. The German Navy also has several other smaller designs that were intended to work in littoral or harbor environments.


Nitpick: Type VII, not IIV.

Otherwise, y’all’ve essentially nailed all the correct answers.

By “underwater” do you mean using diesel engines and a snorkel, or completely underwater using battery power?

I’ve heard that at least with the nucular subs that they are faster underwater. Did this apply to the old diesel boats? Would a diesel boat be faster on the surface than submerged using the diesel engines and a snorkel?

The WWII submarine hull wasn’t optimized for underwater running like a modern sub’s is. My guess is that even with diesels, it’d be slower underwater than surfaced.

There would be no difference to the sub’s speed whether running on battery or diesels. The sub was driven by electric motors, which could be powered from the battery or from the diesel-powered generators. The diesels didn’t drive the boat directly.

The advantage of the snorkel was that running the diesels submerged saved battery power and allowed the battery to be recharged without needing to surface, so that the sub was almost invisible to routine search by ships and aircraft and the battery was kept fully charged for emergencies or combat.

Where are you coming up with “at least two Cold War era US Navy subs,” Stranger? Only two Cold War era U.S. Navy subs were lost, period–the USS Thresher (SSN-593) in 1963 and the USS Scorpion (SSN-589) in 1968. The loss of the Thresher is well-documented and had nothing to do with a torpedo malfunction. One theory for the loss of the Scorpion is indeed a torpedo malfunction, possibly due to a defective battery. However, other evidence indicates that the hull may have imploded only at crush depth, which would not have occurred if an explosion had taken place at normal operating depth.

Loss of depth control due to progressive flooding might very well lead to a hull implosion. There were four water-tight compartments on the Scorpion, and any three could have been sealed, in fact, almost certainly were sealed, as SOP, during a hot-run incident. As the boat sank, each compartment would have lost integrity by some mechanism, including possible hull collapse.

But that’s beside the point. The point is, the Scorpion’s casue of death is still uncertain. A hot-run/battery malfunction in a Mk37 torpedo is by far the most likely, but other possibilties include uncontrolled discharge of the ship’s storage battery (due to shorting caused by failure of the WRT tank, or other sources), and uncontrolled progressive flooding from other sources. In each case, the final shape of the wrecked hull is indeterminate - The Scorpion’s carcass is consistent with a number of possible causes.

WWII submarines were surface ships that could submerge, and fight submerged. they weren’t true submarines, not in the sense that most of us think of. Under water, they were limetd by the power they could safely extract from their storage batteries, and thus were quite limited. They could (nominally) go for roughly 24 hours at a slow speed, or for lesser time at higher speeds. At a flank bell, answering on electric motors, you could completely exhaust the battery in a haour or two.

Snorkelling came later in the war, and was no speed-demon. Sure, you could use your diesel engines, but you lost horspower due to back-pressure on the eshaust, and were limited by the intake air volume, and were further limited by the speed at which you could force your snorkel through the water without bending it over. Also, on the snorkel, you were limited to periscope depth, and made a god-awful racket. Snorkelling was mostly a reaction to being unable to reliably run on the surface for transit to and from patrol stations, and to allow recharging batteries during times when surfacing was risky.

I’ll bet the addition of acoustic torpedoes sure made the destroyer boys a little tighter ass when making their runs. Plus the development of these things makes sense, as I presume a sub isn’t a low cost weapon.

On the other hand, given the detection devices the destroyer had it seems impossible that any targeted sub would ever get away. How did they do this? Given their slow submerged speed how did they ever get out of detection range?

Since the Can had to set the depth on the charges it would almost seem that the sub should have been constantly changing its depth in a sort of sine wave type motion. Or did the destroyer throw out a bunch of DCs set for many different depths?

What a horror being depth charged must have been. Actually it seems like just being on one these metal tubes for an extended time must have been a horror. How in God’s name did they get anyone to volunteer?

Being shot at with no defense or means of return fire was not at all uncommon in WWII. Anyone subjected to artillery fire was in that situation. Aircraft on a bombing run and soldiers being bombarded are examples.

The artillery is three or four miles away and there is not a damned thing to do except rely on chance or be somewhere else.

Submarines were not alone in their fix.

You have to realise just how powerful those depth charge explosions are.

We used to fire our A/S mortars, which are basicly depth set 400lb bombs.

These would fore from the mortars at the stern, right over the front of the ship, masts and all, and land in the sea at a minimum of 1 kilomtre, this was the lowest range setting, they could fire further.

The idea was to direct the mortar fire forwards into the path of the attack sonar, which would be locked on to the submarine being persued.

I can tell you that at minimum range, those charges going off at 1 kilometre away would make the ship kick from the shock, its like being in a tin drum as someone hits it with a sledgehammer.

This is for a surface vessel, you really would not want to be in a sub at one kilometre, I have heard stories that a blast at such a range on a sub is quite sufficient to shock the paint from internal bulkheads.

The images you see on films of a depth charge exploding almost alongside the conning tower of a submerged sub are rubbish, you only need get within 200 yards, that will be quite enough to kill a sub with ease, and at 500 yards with a multiple firing its going to damage a sub, probably sink it.

Even after all this during WW2, and even nowadays, one on one a sub is likely to come out on top against a destroyer. there was an incident in WW1 where one sub took out three cruisers one after the other.

Subs with an adequate supply of torpedos were definately not helpless, the Japanese ‘long lance’ torpedos could take out targets at well beyond 20k yards, allied underestimation of their range proved to be their undoing in many engagements.
Such longer range torpedos were extremely effective against convoys and battle groups.

Now imagine a sub with such weapons, no A/S weapon in WW2 had that kind of range, unless you count aircraft.

Sorry, the other lost sub I was thinking of was the Royal Navy sub HMS Sidon. As has been previously noted, the Mark 37 torpedo carried by Scorpion was an unreliable problem and there were noted problems with battery failures that could have caused a hot run scenerio or a fire/explosion. It was my understading that there was a acoustic track indicating the sub doing a 180 maneuver (which could either be an evasive maneuver to escape a release hot-running fish, or activate the safeties to prevent it from arming) but the author of the Wikipedia article on the topic claims that the data is too garbled to extract such information. At any rate, hot-running torpedos were a known problem to the extent that there were established procedures how how to disable or dump them. The Russians may have lost one or more subs to torpedo failures as well–they certainly lost a bunch, though many are suspected to be reactor failures–but the only one known about is the Kursk in 2000, and even that is speculation.

Subs got out of detetion range by diving too deep to be seen and moving quietly out of range. You have to remember, at least in the Atlantic war, the primary objective of the Kriegsmarine was to attack convoys, and the objective of the US and Royal Navy was to protect convoys bringing critical supplies for Britain and later the Allied forces in Europe. Driving a submarine away from a convoy wasn’t as good as a kill, but it was often “good enough”, especially since you couldn’t always be sure whether you’d made a kill or not. This is part of the reason subs hunted in packs; one would attack, drawing escorts away, and then other subs would settle in under the convoy and then surprise attack just when everybody was feeling nice and safe.

Standard practice was to vary settings on the depth charges; the best thing for a sub commander to do was dive deep, change direction, and move out away from the convoy far enough that the escort wouldn’t follow. As previously stated, depth charges were rarely effective in actually killing a sub, but they were a great harassment tool and sometimes you could force the commander to panic and do something stupid, or at least luck into doing enough damage to make a sub nonoperational.

Sub duty was prestigeous work, particularly for the German Navy that was otherwise disdained by Hitler and his crowd. The Germans never had a particularly notable surface navy (despite defeating a Royal Navy squadron in the Battle of Coronel, and giving better than they got at Jutland), and after WWI they were hobbled by restrictions in the Treaty of Versailles, so instead they focused their marine warfare strategy on submarine forces intended to destroy transAtlantic supply lines. It was a good strategy for the cash-strapped and nearly landlocked Germany, and one adopted in large measure by the Soviet Union in a Warsaw Pact versus NATO conflict. Also, the German Navy was one area of the military that was not dominated by the Nazi Party and infiltrated by the SS; again, Hitler’s people were less than interested, so if you wanted to serve the Vaterland with minimal arm waving and mouthing fascist slogans, the Navy was the place to go. Many naval captains didn’t even belong to the Nazi Party, in contrast to high ranking officers in the Army and Luftwaffe. Das Boot actually illustrates this; the political-officer type is regarded by other crewmen as a degenerate, useless swine, and there’s a hilarious joke where they find pubic lice in his eyebrows (after finding another crewman infested in the more typical location).