Siege of Westerplatte and German naval gunfire

[PeZook]

I have been meaning to write this for some time now.

Some background first: The Siege of Westerplatte was an engagement from 1-7 september 1939 in the Danzig Free City, fought between German troops (of various branches) and a Polish garrison of the military transfer warehouse as part of the September Campaign.

During the engagement, the Polish garrison withstood repeated assaults supported by a truly massive assortment of artillery for such a small operation, plus repeated air attacks, inflicting a total of 300-400 casualties (dead and wounded) to the loss of about 20 dead and 50 wounded, it's one of the defining battles of the september campaign known to every Polish child etc etc etc.

Here's the crux of my question, though. During the siege, the Germans have assembled the following artillery assets that bombarded the outpost:

1. The Schlezwig-Holstein battery

Schlezwig-Holstein was a predreadnaught which anchored in Danzig's Northern Port under the guise of a ceremonial visit, but its true purpose was to provide naval gunfire support for the assault on Westerplatte. Its battery consisted of:

4x 280mm guns in two turrets
14x casemated 170mm guns
22x 88mm naval guns, also casemated

2. Mortars

2x 211mm mortars
Unknown number (at least 2) of 170mm mortars
81mm mortars

3. Field artillery

35 light artillery pieces, including an unknown number of 105 and 210mm howitzers.

4. Air support

40-60 Stukas

---

All of this artillery was used to bombard this strip of land.

You can see here the position of the battleship, and the arrangement of Polish defences. These fortifications were rather light.

You had a ring of small blockhouses:



These housed several soldiers, had reinforced concrete walls and a cellar equipped for defence.

There was one proper bunker (the "Fort" outpost, seen on the map and arranged towards the sea) as well as two large buildings: the barracks and officer's quarters, also equipped with reinforced cellars).

The outpost was manned by 225 soldiers equipped with a disproportionate amount of machine guns, as well as several mortars and a 75mm field gun.

These assets were able to defend the outpost against repeated German assaults for seven days. There were 13 separate firefights. Artillery bombardment and air strikes were pretty much constant. Yet, Polish casualties to artillery fire were slight: one soldier dead due to shrapnel on September 1st (two separate bombardments by the battleship, two infantry assaults) and several dead on September 2nd in blockhouse no.5 which received a direct hit. One blockhouse received a near-miss by a 211 or 170mm mortar, but otherwise they were untouched. The barracks were hit once by an aerial bomb - again, no serious casualties.

It seems almost comical ; The constant shelling did not compromise Polish defences at all, and they were able to repulse all attacks, including the final one on September 7th which included flamethrower-armed infantry. Yet, seeing the position of the battleship (less than a kilometre away from all targets!), one would think the Germans should've been able to methodically destroy every single Polish emplacement using fire control no more complicated than spotters on the ship itself!

So, what gives? What could've caused this stagerring ineffectiveness of German fire support against a lightly fortified target?

[CaptHawkeye]

Naval gunfire had historically proven pretty ineffective without land-spotters to direct fire onto targets. A ship will quickly obscure what it's shooting at with smoke and dust if it engages targets directly. The British for example were unable to neutralize the defenses of the Dardanelles Straight with naval gunfire, even though they could clearly see them. Every fort guarding the Straight still had to be seized by infantry.

I doubt the Germans had the kind of equipment and training necessary to direct naval fire onto targets from the shore either. Even if they could see what they were shooting at. The US managed to use naval gunfire to extreme, often devastating effect during the war, but the resources, training and coordination were there. It took practice too, and naval gunfire still never became an end-all solution.

The Westerplatte is tiny sure, but so were Tarawa, and Peleliu and massive bombardments from almost every toy the US had didn't reduce the defenders to impotence in those places.

[Sea Skimmer]

The naval gunfire was at point blank range, which is precisely the problem, the grazing angle is so low it turns into the shells ricocheting into the air most of the time and being completely ineffective. They may not detonate at all even as they spin away in the air.

Only a direct hit on the bunker wall itself will do anything in this situation, as the shells aren’t going to dig into the ground beside them and detonate, and at such close range it may not even be possible to adjust obsolete battleship guns in the tenths of mils required to accurately hit such a low profile target. The normal sighting equipment on artillery is generally not accurate enough to do this, you actually have to get out a gunners quadrant and do it manually. Higher angles of fall are more desirable as they reduce the ricochet problem, though range will rapidly increase dispersion.

Also the entire area was forested, and partly surrounded by a wall, so it’s unlikely that the Germans could in fact see anything they were shooting at from the ship itself, or most observation points for that matter. After the first salvos so much smoke and dust is thrown up your shooting blind anyway. Firing from a longer range with aerial observation that was first coached onto the target area with ground directed mortar fire would have almost certainly been more effective. Such techniques are unlikely to have existed in the German navy. It was also important to conduct such destruction missions (and all artillery destruction missions) with just a single gun. Generally your least worn and thus most accurate gun. This way you have very precise control and adjustment of your fire, and you minimize the dust and smoke of wasted rounds.

Estimates were in world war one, I have a chart of this around somewhere, that it took five hundred to seven hundred rounds from superheavy railway artillery to knockout a single pillbox or casemated artillery position at long range. Similar amounts of ammunition were required for heavy and medium guns to knock out enemy field guns in pits in the open at shorter ranges. Making a 25 yard wide breach a single belt of barbed wire could take three hundred to five hundred 75mm shells. They didn’t fire nearly 1 billion artillery shells in WW1 for no reason.

The air raid seems to have been singular, and did about what I’d expect, a few positions knocked out, much disruption. Even dive bombers with no AA fire would struggle to have a CEP better then 100m or so, but a 500kg bomb at 100m will do nothing to even a light bunker. You need a hit within maybe 15-20m or less to destroy a light one. Even earth and timber bunkers can resist massive proximity explosions if well constructed, and the Poles were not bad military engineers. The field works they had years to prepare were probably very strong. It’d be foolish at least to think otherwise, though the high water table would preclude deep shelters.

Given the small number of artillery pieces employed, fired seemingly indifferently over multiple days at various targets, the level of destruction is actually about what it should have been. particularly when the attacker is green.

Artillery mainly works against fixed defenses by disrupting the enemy and suppressing him, not destroying him. If you cannot exploit that effect then you accomplish little except destruction of barriers. The USN and British took this to heart after early amphibious problems, creating massively armed barrage rocket ships, and later landing craft armed with batteries of heavy mortars, and large numbers of close support ships. More or less floating tanks. Besides the actual floating tanks. This is with invasions being backed up by tens of thousands, hundreds of thousands in some case, of naval shells. The Germans fired hundreds.

Meanwhile all of the attacking German troops were green; relatively few of them appear to have actually been highly trained infantry, so the overwhelming force needed to assault a defense with major natural obstructions and constructed avenues of approach just doesn’t seem to have been present. In fact it appears the main German assault group may have been only marginally larger then the defenders. Not that surprising, considering the constricted approach.

Once that main assault force was battered in its first attempt, I’d speculate its moral never really recovered, and with word that Poland was collapsing, nobody felt any great élan to go try again. This tends to happen in battles, if the attacker does not see a point to his struggle each new effort will be less effective then the last. You can still win like that by progressively weakening the enemy, but it will be slow. Seems to fit the facts.

What was needed for a quick victory was either much more concentrated artillery fire, shot until each specific target was destroyed (if you stop you loose all the accuracy you gained from careful adjustment as the barrel cools off and weather shifts) or a direct fire weapon brought up under cover of indirect artillery to destroy the positions. This is a major reason why the Germans initially designed the Tiger tank, and heavily used towed 88mm flak guns against other Polish fortifications and the minor works of Maginot line they dared assault. In this case, the attackers seem to have been unable to do so because of the constricted approach and trees, or just from lack of any plan or assets to do so.

This very kind of situation after all, is why the tank was invented in the first place.

[PeZook]

Thanks a lot for the detailed explanation, Skimmer. That certainly puts the issue to rest.

I actually thought the forest and the wall could have had something to do with the problem ; I'm not sure if the place was deliberately forested, but it's actually pretty likely - it was, after all, in the middle of territorry which was German in all but name. And the Germans did try to burn the forest down on several occasions, first using railways cisterns filled with gasoline and later a more sensible plan involving flametrowers (which actually worked, unlike the cisterns), so it should've been obvious that they considered it a serious problem, yeah.

However, I figured that even if ship-based spotters would not be able to pull this off, ground troops should've been able to direct fire onto the defence emplacements, at least those that were firing at them - especially since they had days to do it, and in between major assaults, patrols would constantly probe the defences. But that's a more complex fire control problem, and especially with green troops cobbled together from what was available for a minor battle on the sidelines, they might not have had the training or equipment to pull it off.

The naval gunfire was at point blank range, which is precisely the problem, the grazing angle is so low it turns into the shells ricocheting into the air most of the time and being completely ineffective. They may not detonate at all even as they spin away in the air.

You know, at first I wanted to ask if the Germans should know about this, since it's probably not something especially new or surprising to people who deal with artillery, but then I realized something else: they might've been concerned about firing on the Westerplatte from longer range (which would necessitate firing from the sea), because it was literally right next to important port facilities.

Later on during the battle two torpedo boats began shelling the place from the sea, but a few shells overshot and blew up a bunch of fuel cisterns sitting on a railway siding. Now these were just small ships, imagine if a couple 280mm overshot the place!

So they might've felt it was the only way to do it without wrecking half of their own sea port, despite all the shortcomings of firing point-blank.

The air raid seems to have been singular, and did about what I’d expect, a few positions knocked out, much disruption. Even dive bombers with no AA fire would struggle to have a CEP better then 100m or so, but a 500kg bomb at 100m will do nothing to even a light bunker. You need a hit within maybe 15-20m or less to destroy a light one. Even earth and timber bunkers can resist massive proximity explosions if well constructed, and the Poles were not bad military engineers. The field works they had years to prepare were probably very strong. It’d be foolish at least to think otherwise, though the high water table would preclude deep shelters.

Some sources say there were two air raids, but it's unimportant: it occured to me that I kinda understated the value of the first airstrike on the 2nd day. It may have knocked out only a single blockhouse, but it caused so much disruption that had it been closely coordinated with an infantry assault, Westerplatte would've most likely fallen right then and there. AFAIK no assault was undertaken because Germans were still unsure just how fortified the place was, and some information they had indicated there was an extensive bunker complex, etc.

Meanwhile all of the attacking German troops were green; relatively few of them appear to have actually been highly trained infantry, so the overwhelming force needed to assault a defense with major natural obstructions and constructed avenues of approach just doesn’t seem to have been present. In fact it appears the main German assault group may have been only marginally larger then the defenders. Not that surprising, considering the constricted approach.

Don't forget the defensive force was seriously overstrength and overarmed for a garrison company: they had around 220 men and something like 40 machine guns alone, at least a thousand grenades, mortars, a field gun etc - so it's really no surprise the ground part of the siege went like it did.

[Sea Skimmer]

However, I figured that even if ship-based spotters would not be able to pull this off, ground troops should've been able to direct fire onto the defence emplacements, at least those that were firing at them - especially since they had days to do it, and in between major assaults, patrols would constantly probe the defences. But that's a more complex fire control problem, and especially with green troops cobbled together from what was available for a minor battle on the sidelines, they might not have had the training or equipment to pull it off.

They might not have even had a radio that could actually talk to the ship in a direct manner.

Incendiary mortar fire or bombing might have burned the forest more easily, were it available. Probably wasn't. This is really a situations in which the best indirect support would have come from heavy mortars, but such weapons could only be found in select German chemical mortar battalions at the time. The mention of '17cm mortars' may indicate they had a few of the WW1 era infantry mortars around though, as no other 17cm weapon of any sort was in German land service in 1939 except for a few railroad guns. Or that's just mistaken, so many accounts of German artillery are.

You know, at first I wanted to ask if the Germans should know about this, since it's probably not something especially new or surprising to people who deal with artillery, but then I realized something else: they might've been concerned about firing on the Westerplatte from longer range (which would necessitate firing from the sea), because it was literally right next to important port facilities.

Firing from almost any other angle would risk shells landing on German troops if nothing else. Also, everyone overrated naval gunfire without practical experience, and tended to be dismissive about artillery in World War One in the early war period.

I couldn’t find the chart I had in mind, I did find a different one which among other things indicated that 80 rounds from a 9.2in howitzer were estimated to be required to destroy a basic earth machine gun emplacement with a roof made from six wooden beams. This is assuming direct observation and adjustment of fire.

Some sources say there were two air raids, but it's unimportant: it occured to me that I kinda understated the value of the first airstrike on the 2nd day. It may have knocked out only a single blockhouse, but it caused so much disruption that had it been closely coordinated with an infantry assault, Westerplatte would've most likely fallen right then and there. AFAIK no assault was undertaken because Germans were still unsure just how fortified the place was, and some information they had indicated there was an extensive bunker complex, etc.

You’ll find that in many situations when troops are faced with a fortified opponent. They’d rather wait for the enemy to be destroyed by supporting arms. Sometimes it’s a good idea, other times it just leads to heavier losses. The 1943 US invasion of Makin Island was a good example of this; though US forces in general were extra prone to it since our commanders very much knew we had lots of material to expend.

[aieeegrunt]

The Schlezwig-Holstein was classified as obsolete and useless by the German navy in 1916. It spent the rest of WWI as either a target for Uboat training or anchored in the mouth of the Elbe as a coastal defence battery. This is probably why the French allowed the Germans to keep it at Versailles. It got a refit in 1926, but was again classified as useless and relegated to training duties in 1936. I cannot imagine that her gunnery was all that effective or useful even without the usual problems with shore bombardment.

You can actually find a youtube video of the S-H bombarding Westerplatte, but it's mostly clouds of smoke.

[Sea Skimmer]

Her role in most of the interwar period including 1939 was that as a officer training ship, meaning that she would have had some of the better people in the German navy on board as instructors. Being obsolete has very little bearing on this, after all most of the US ships used for shore bombardment in WW2 were not much older. The issue remains that the methods needed for effective shore bombardment were simply not the same as those to engage moving ships.

The Germans were allowed to keep six predreadnoughts under Versailles, even though they were far larger then the allowed 10,000 ton limit for new construction, because the British and French wanted the Germans to have some kind of ability to bottle up the Red Commie Fleet in the Baltic at the time. By 1939 only two remained in an armed role, the others had been broken up or converted to targets ships.

[Raesene]

I'm not sure Schleswig-Holstein still had all the guns listed onboard, that list reads more like the state upon first comissioning.

Had a lok at the german wiki entry for the ship, that provides a different set of artillery:

4 × Sk 28,0 cm L/40
6 × Flak 10,5 cm (1.800 rounds)
4 × Flak 3,7 cm
4 × Flak 2,0 cm

more in line for a training vessel, more modern, and much lighter than the previous list.

Not having the the 17cm and 88mm guns makes the difficulties more plausible in my opinion, especially the 88mm guns were fitted for torpedo boat defense, they should have been able to hit small targets quickly.

[Sea Skimmer]

She definitely had at least some heavy secondary guns remaining, though they were most likely 15cm rather then 17cm at this time. You can see them trained out and firing in the film of the attack. The caliber difference would be functionally meaningless. I've also read accounts of training on board one of this ships which was explicit about heavy secondaries being used to form training gun crews.

Interestingly you can also see in the film that the ship had a tug standing by her that clearly repositioned her several times. Plainly she’s firing directly into a forest and its doubtful that even an observer at the masthead had any clue where the fire was going.

Most if not all of the 88mm guns were removed, some positions are plainly empty, and its no surprise since such guns were functionally almost useless anyway. Certainly completely useless in the self defense role. The positions for such weapons were always terrible, like bow and stern casemates, and firing them rapidly precluded even an attempt at aiming, which defeated the point of mounting such a rapid firing gun. Such weapons were generally being removed while WW1 was still going on. They only really made sense in the late 19th century when torpedo ranges were incredibly short, and the torpedo boats so small that a single hit or even canister fire was effective. Such mounts also never had any form of fire control except possible range and order telegraphs.

I will partly retract what I said earlier though. While it doesn’t really matter that the ship was obsolete, the ammunition for the main battery being so old may have reduced accuracy. At least, if the gunpowder was really old it wouldn’t help things. The shells would be fine. Functionally I can't see it mattering. The film is even more blatant then I ever recalled about bombarding into the woods.