Her Majesty's Silent Service - An improved RN submarine force in Second World War

Part 19 - Germans reinforce Norway - 12 April 1940 - Unternehmen Brauerei
Part 19 - Germans reinforce Norway - 12 April 1940 - Unternehmen Brauerei

The operation to reinforce Norway, Unternehmen Brauerei, was something in which Germany excelled compared to the Allies at this early stage of war - improvising and adapting. The submarine threat to reinforcement convoys was deadly and in the West coast of Norway surface threat would be great.

Air transportation efforts would have to suffice for Bergen, and Stavanger after Sola airfield had been repaired to operational use. This transport effort would mainly compose of 2. Gebirgs-Division. Trondheim and Narvik would have to manage by themselves with some submarine delivered special supplies to be arranged at later date.

Thus the next echelon of German troops to Norway would be transported in heavily escorted convoys which would pass the most dangerous area between Laeso in Kattegat and Oslofjord in daylight. The first convoy which would run to Oslo would transport 181 Infanterie-Division, followed by three other infantry divisions on roughly three day intervals.

Kriegsmarine would provide distant cover with submarines. Luftwaffe would finish any surface attempts to interfere. Surface forces, although greatly weakened, would finish any leakers trying to interfere with convoys. The convoys itself would be heavily covered by a large number of U-jägers (ASW trawlers) of 11., 12. and 17. Unterseejagdflotille. which would limit their speed but would provide protection. Ships in convoys themselves would be large and modern merchants which would be capable of better sustaining damage than older ships. The convoys would also have air cover by Luftwaffe He-115 units all the way.

U-jäger Uj-113 struck a mine laid by French submarine Rubis near Laeso on 0345 12 April 1940. This was the beginning of a battle which would be the first between a co-ordinated submarine group, Steelforce with 4 Overseas boats, and a defended convoy.

Meanwhile, the Allies were still preparing for their land forces to get in. And they were thinking in terms of battalions and brigades, not divisions.
 
Part 14 - RN submarine dispositions on 8-9 April 1940
An interesting tail so far, albeit with a handful of proofing errors.

This one is interesting, though. The placement of the Submarines suggests that Horton may disagree with the higher echelons in the Admiralty about this being a mass breakout.

Is this the case? Or was it simply too late for him to move the boats to screen for a breakout into the North Atlantic?

If he does disagree with the Sea Lords, why does he believe it's an attempt on Norway? Gut? That's what he's been planning? ORP Orzel's report? A combination of the above?

Keep up the good work!
 
Meanwhile, the Allies were still preparing for their land forces to get in. And they were thinking in terms of battalions and brigades, not divisions.
With the German surface fleet destroyed the Allies are probably thinking truly massive levels of Naval Gunfire Support trumps whatever troops the Germans have managed to land.
 
Logistics. logistics, logistics , without being able to use sea transport , Norway's transport network is to put it mildly rubbish. You get so far up and the rail stops ( then restarts further up ). Given the year , air transport cannot do much at all tonnage wise and the roads are interesting outside the south ( and that's in summer ).
Allies would have thought battalions and brigades because that's all they would need to hold their primary objective, Narvik ( and supplying larger forces would be fun ). With most of the big ships lost and the transports captured, the German troops in the North will not last long , its not a place were living off the land works well. Got to remember in pre container days, ships take a long time to offload supplies,so most of them for the Northern groups will be either captured or at the bottom of a fjord.
 
An interesting tail so far, albeit with a handful of proofing errors.

This one is interesting, though. The placement of the Submarines suggests that Horton may disagree with the higher echelons in the Admiralty about this being a mass breakout.

Is this the case? Or was it simply too late for him to move the boats to screen for a breakout into the North Atlantic?

If he does disagree with the Sea Lords, why does he believe it's an attempt on Norway? Gut? That's what he's been planning? ORP Orzel's report? A combination of the above?

Keep up the good work!

Thanks! On various proofing and maybe some other slight errors I've decided to get on with writing, rather than try to polish every piece. After all, it's writing for my enjoyment, not a dissertation. I'm more than happy with anyone pointing errors whether in continuity or other issues.

On basis on limited reading I've made, in OTL Horton correctly - in hindsight - deduced that Germany would counteract the Allied Operation Wilfred with an expedition to Norway. In TTL he does the same, but with slightly more operational independence due to earlier success and slightly larger number of available boats he manages to keep the disposition to prevent invasion instead of being made to sent the boats away to form patrol lines to support the Home Fleet operations.

With the German surface fleet destroyed the Allies are probably thinking truly massive levels of Naval Gunfire Support trumps whatever troops the Germans have managed to land.

Yes, close to shore, especially in Narvik (as OTL) and in Trondheim (TTL).

Allies would have thought battalions and brigades because that's all they would need to hold their primary objective, Narvik ( and supplying larger forces would be fun ). With most of the big ships lost and the transports captured, the German troops in the North will not last long , its not a place were living off the land works well. Got to remember in pre container days, ships take a long time to offload supplies,so most of them for the Northern groups will be either captured or at the bottom of a fjord.

What the Allies have now, is a real chance not to hold only Northern Norway but the whole Norway (which, incidentally, makes holding Northern Norway a tad more easier). It remains to be seen whether they can grasp their chance...
 
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Part 20 - The Convoy will always get through - 12 April 1940
Part 20 - The Convoy will always get through - 12 April 1940

The protection scheme for the first reinforcement convoy was, although improvised, quite elaborate. It is presented here as it set the pattern for further German convoys to Norway, with ever increasing efficiency of escorting forces. He-115 floatplanes would reconnoitre the convoy route in advance, with at least one on call over the convoy at all times.

At this date U-Jägers did have just passive listening devices with only some warships having the German ASDIC, S-Gerät. The depth charge loads of escorts at this stage were rather small, and they did not have the elaborate DC thrower and ASW rocket systems of the later date. Strength of the close escort was 40 U-Jägers, 10 Vorpostenboote for flak and against light forces and 10 R-boote. R-boote were convoy commander's reserve to be sent where U-jägers had made contact.

The German strength at this early stage of war was the ability to concentrate forces instead of spending them in penny packets. Heavy escort ensured, that a contact could be pursued to a kill without weakening of the protection. The heavy escort consisting of slow trawlers limited the convoy speed to about 7 knots, though.

The German convoy itself consisted of 12 ships with average of 7000 tons. Typical of German reinforcements convoys to Norway the ships themselves were of extremely good quality, mainly diesel cargo liners with double decks and good amount of derricks and cranes, as Germany did not suffer from lack of tonnage due to blockade at this early stage of war. Typical representant of the fleet was MS Wuppertal of Hapag, 6700brt, diesel-electric propulsion, built in 1936. The fairly large amount of tonnage in good quality shipping would ensure that units could be combat loaded for rapid disembarkation.

Only two Steelforce group submarines catched a glimpse of the convoy due to the fact that they had to mostly stay under water due to heavy air cover. According to German reports two salvos of torpedos were spotted, which sank one ship and damaged one other. Both HMS Triumph and HMS Tarpon were sunk without survivors. Two other submarines of the group could not manage to get into attack position and they were directed to take an ambush position close to entrance to Oslofjord, which was incidentally patrolled by very active U-jägers.

The 181. Infanterie-Division and two-company strong Panzer-Abteilung 40 (one of the companies had been sunk by submarine on 10 April) thus arrived in Oslo with fairly light casualties. The first battle between an heavily escorted convoy and a group of submarines was over. The submarines had lost. But a campaign consists of a series of battles instead of one battle.
 
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Part 21 - The Allies prepare for a counterblow - 13 April 1940
Part 21 - The Allies prepare for a counterblow - 13 April 1940

On basis of submarine sent reports and also some signals intelligence Horton received the news - or lack of them - from the boats sent to attack the German convoy. In an effort to interdict traffic between Norway and Denmark submarines alone would not suffice. The next effort would rely first on either RAF Coastal Command or submarine reconnaissance efforts and then a surface attack to scatter the escorts.

The Home Fleet approved the plan and was delighted that the French would take brunt of the surface interdiction task which would surely entail heavy casualties. Thus Groupe Z, with cruiser Emile Bertin and nine destroyers under command of Vice-Admiral Edmond Derrien, would be the ones charging to Skagerrak when ordered. This was also easier for the French, as everyone firing white would just be the enemy.

In case Oceangoing type was too large the next effort would consist of smaller Home Service type submarines used en masse. Six new V’s would form a patrol line closest to Oslofjord. Although not yet fully trained, they had the best batteries to stay underwater for most time. Four older would be ready to attack while two best trained subs would intrude right towards Copenhagen, passing Anholt both from Western and Eastern dimensions.

The staff estimated, correctly, that the next German convoy would be sent on 15 April 1940 possibly consisting of different ships than the first convoy but utilizing same escorts. With ample German tonnage available it would be of no use attacking a returning convoy.

On 13 April 1940 a number of submarines which had been recalled earlier set sail from Rosyth. Onboard two Oceangoing boats coming from the Mediterranean was the new B Squadron, SBS. Onboard four Home Service types were two torpedos and twelve magnetic mines.

In the far north HMS Warspite, with help of nine destroyers finished up German warships in Narvik. Germans were now completely bottled up with no hope of help. Elimination of any German surface threat released a number of surface combatants as well as aircraft carrier HMS Furious to a more southern destination.
 
The German convoy itself consisted of 12 ships

the close escort was 40 U-Jägers, 10 Vorpostenboote for flak and against light forces and 10 R-boote.
:eek::eek::eek: For a convoy of 12 merchantmen?:eek: That seems mighty heavy to me.
they had to mostly stay under water due to heavy air cover
I'm wondering if weather wouldn't offer at least some opportunity.
According to German reports two salvos of torpedos were spotted, which sank one ship and damaged one other. Both HMS Triumph and HMS Tarpon were sunk without survivors.
So how did they achieve firing positions without being detected, given so much air cover? How did they just happen to be just in the right spot(s)? And if they're placed at the mouths of fjords (where I'd put them), why aren't there more Brit boats present? And why can't they sneak in & shoot as the Germans are unloading? (That's what I'd do, were I a Brit sub CO.)
 
:eek::eek: For a convoy of 12 merchantmen?:eek: That seems mighty heavy to me.

If the invasion almost failed due to sub threat, they're going next with all the resources they can gather. The craft involved are, after all, armed trawlers, not purpose built escorts.

So how did they achieve firing positions without being detected, given so much air cover? How did they just happen to be just in the right spot(s)? And if they're placed at the mouths of fjords (where I'd put them), why aren't there more Brit boats present? And why can't they sneak in & shoot as the Germans are unloading? (That's what I'd do, were I a Brit sub CO.)

If there's enough subs in fairly small area, some are bound to get into firing position. A convoy makes a lot of noise which enables firing position to be reached under water even with primitive underwater range of the subs at the time. The mouths of the fjords are the obvious places - that's why German would patrol them aggresively. As for getting into harbor, the Oslofjord is very narrow and German have mined the Drobak sound guarding the entrance to Oslo harbor with remote controlled mines. It's just a few hundred meters wide.

But then again, there's other kind of Royal Navy thingies which carry torpedoes and can get over any obstacles...
 
If the invasion almost failed due to sub threat, they're going next with all the resources they can gather. The craft involved are, after all, armed trawlers, not purpose built escorts.
There's still 40 of them for a convoy of 12 merchantmen, & that's a lot, more than I'd expect under any but "this convoy is crucial to survival" kinds of conditions.
If there's enough subs in fairly small area, some are bound to get into firing position. A convoy makes a lot of noise which enables firing position to be reached under water even with primitive underwater range of the subs at the time.
At 2kt? Against a convoy doing 7? Without the ability to surface & pursue (which you've effectively ruled out, tho I'm not completely convinced an aggressive skipper might not get around it)? Don't bet on it. Subs at that time were little more than slow-moving minefields; unless the convoy effectively ran right over one of them, the chance of achieving a firing position submerged was nearly nil. And using up battery to increase submerged speed means losing no small part of the power needed to evade after an attack, when the escorts are chasing you, which is not an ideal time to be short on battery power.
The mouths of the fjords are the obvious places - that's why German would patrol them aggresively.
They're also the only places a hostile sub can be certain a convoy must pass, making them ideal for attacks. "Aggressive patrolling" may detect a dived sub, or may not; being even a mile or two out of position when a convoy passes, you lose your chance.
As for getting into harbor, the Oslofjord is very narrow and German have mined the Drobak sound guarding the entrance to Oslo harbor with remote controlled mines. It's just a few hundred meters wide.
Penetrating a minefield isn't out of the question...but I'll concede the hazard may not be worth it.
 
There's still 40 of them for a convoy of 12 merchantmen, & that's a lot, more than I'd expect under any but "this convoy is crucial to survival" kinds of conditions.

At 2kt? Against a convoy doing 7? Without the ability to surface & pursue (which you've effectively ruled out, tho I'm not completely convinced an aggressive skipper might not get around it)? Don't bet on it. Subs at that time were little more than slow-moving minefields; unless the convoy effectively ran right over one of them, the chance of achieving a firing position submerged was nearly nil. And using up battery to increase submerged speed means losing no small part of the power needed to evade after an attack, when the escorts are chasing you, which is not an ideal time to be short on battery power.

The area of operations is very small, so there's only a certain possibilities what routes to take which increases the chances for a sub attack, even though sub may have only a limited amount of manouverability. Of course to fully explore a situation I would have to wargame it, so there's artistic license.

Penetrating a minefield isn't out of the question...but I'll concede the hazard may not be worth it.

Remote controlled minefields of the time usually included an anti-submarine indicator loop, ie. magnetic detector. The basic idea was, that the submarine was first detected by microphone and when indicator says "beep" you press the button and the mines say "boom". For larger subs it's effectively an inpenetrable barrier on narrow straits.
 
Part 22 - 14-15 April 1940 - Raids
Part 22 - 14-15 April 1940 - Raids

One should not bring a knife into a gunfight and one should not try to fight proper surface combatants with converted civilian craft.

The French Groupe Z’s raid on German convoy on 14 April 1940 was a total success. Thanks to weather the force managed to slip by German U-boats and air reconnaissance. The first warning German convoy received were the green and pink pillars of waters emerging among the outer escorts as the Groupe Z charged at 35 knots.

The converted trawlers were totally outmatched against the eight modern destroyers and the light cruiser Emile Bertin. Just five of the escorted merchants managed to slip towards north while seven merchants succumbed under the waves after receiving hits from torpedoes. Casualties among the escorts were surprisingly low - just ten sank and eight damaged - as the Groupe Z was focused on destroying the convoy, not escorts which were not of any value. From the first shot fired to the last the whole raid lasted just for some fifteen minutes during which Emile Bertin received just two hits with destroyers unscathed - skills of German reserve gunners were low. Unfortunately on the way back destroyer Bison got hit by Luftwaffe bombs and was sunk.

Five escaping merchants did not have luck either, as three of them caught torpedos shot by RN submarines. In the end, just two merchants got into Oslo. 196. Infanterie-Division had been effectively destroyed.

The night between 14-15 April 1940 introduced a new kind of anti-shipping measure to warfare as well, as Swordfish torpedo bombers from HMS Furious struck Oslo. Four merchants were sunk pierside, effectively taking large amount of harbor out of use in addition to disabling a large number of supplies.

On midnight between 14-15 April 1940 the Åalborg airfield was in the receiving end of a raid by a canoe born raid by B Squadron, SBS. The raid could be characterized nasty, brutish and short resulting in a number of destroyed JU-52 transports and above fuel trucks and the bomb depot. The extraction on 16 April 1940 was successful with total casualties from the raid being just four KIA.

On night of 14-15 April 1940 the usage of magnetic mines was also started by the Allies, as air laid mines were dropped to Kiel bay and submarine laid mines to Kattegat.

German forces in Trondheim were surrounded by Norwegian forces which were, although lightly armed, capable of keeping the perimeter. With the arriving British 146 Territorial Brigade and French 5e Demi-Brigade Chasseurs Alpins starting from 15 April the life expectancy for the garrison would be rather low. In the end it was the timidity of the Allies which kept the garrison from surrendering already.

In Narvik the British 24 Guards Brigade started to land on 15 April 1940. 24 Brigade would be the only initial Allied force in the far north as the brunt of reinforcements would be directed to Trondheim area. 24 Brigade and 6th Norwegian Division would be more than enough to make the Germans stay put.

In Oslo the German forces were preparing to advance towards Trondheim in order to relieve the forces there. A force comprised of two infantry regiments and Panzer-Abteilung 40 would start it’s drive towards north on 16 April, supported by tactical landings of company size by paratroopers, if everything went as planned.

But in the end what was really critical about Norwegian campaign was the break given for Norwegian Army thanks to delay for German reinforcement schedule. Every day and every hour enabled Norwegian Army to complete the incomplete mobilization possible, to dig in and above all, to prepare the forces for active measures modelled after what had happened in Finland the previous winter. German forces were few in numbers and with very vulnerable supply routes.

At the same time Luftwaffe was reappraising the situation in Norway. The campaign in the West would begin in some three weeks and the forces would need some time for redeployment and recuperation before Fall Gelb, the battle of survival for the Third Reich. Should there be any reason why Luftwaffe success in the West should be sacrificed for Kriegsmarine boondoggle in the North?
 
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