Why couldn't iron ore from Sweden be transported just through the Baltic Sea?

I really think your explanation is worthy of attention. I have a similar hypothesis myself. I just wouldn't quite agree that there was not much the British could have done to transport it through Norway. They could and did, and there were considerable losses. Here I think it is likely that Hitler was hoping to occupy Britain, or at least make peace. And when he attacked the Soviets, he thought he would get everything he needed from there. And then,as you also mention, it was no longer a matter of concern nor an opportunity. The only question is how realistic this project could have been. Maybe it was not really possible at all, because of the geography of Sweden or something else.

 

Ewen beat me but a couple addition
A short article shows how long it sometimes took to build up a railway in Northern Sweden Inland Line - Wikipedia
a more general history of the railways in Sweden with a good map on the situation in 1910, after that not very much happened but the Inland Line before the WWII. History of rail transport in Sweden - Wikipedia

 

Loads of interesting stats in the tables in this article. Note the reduction in tonnage from Narvik to Germany in table 5a. (Thousand tons)

1939 4027 from a total of 5866 total export from that port
1940 504 from 1266 total export from Narvik
1941 725
1942 1140
1943 1936
1944 1106
From 1941 100% of exports from Narvik were going to Germany

Despite the significant decrease in tonnage moved via Narvik Table 5d shows how it increased in importance as the war went on accounting for 6% in 1940 but 30% in 1944. But by 1944 exports to Germany were only about one third of their 1939 levels.
https://www.tandfonline.com/doi/pdf/10.1080/03585522.1965.10414365

By 1944 allied political pressure saw a shift in Swedish attitudes to continuing to supply Germany. Add to that that from Sept 1944 when Finland switched sides, Soviet submarines could begin to roam more freely around the Baltic

 

In addition to the excellent articles posted by Ramiles, Ewen Scott and Juha, for any of you interested in the Swedish Malmbanen ("Iron Railway") - the means of getting all that lovely iron ore out of the mountains and down to the sea - I have the following articles:

Lapland's Arctic Railway - Wonders of World Engineering
This is very useful for giving some idea of the scale of the mining and the ensuing works . . .

Signalling down the mine - Rail Engineer
Too modern for our period, but useful background info all the same

To reinforce my point about the geography of northern Sweden and its suitability (or not) for railway-building, I've found a gradient map of the line which gives some idea of what the engineers had to do to make a workable railway from the mines to the sea. Kiruna is 530 metres (1738 ft) above sea level and it is 170 km by rail down to Narvik, or 300 km down to Luleå - the nearest reliably ice-free port seems to be Oxelösund, just south of Stockholm, which is 1,200-1,300 km away.

The main thing that emerges from these articles is that, due to its lack of coal, Sweden became a pioneer in the use of electricity as a source of power for railways - particularly, in this case, to power a very heavy haulage line. The various locomotives used on the Malmbanen were leaders in their class throughout their history, being amongst the heaviest and most powerful in Europe, if not the world. The ore cars were similarly heavy and specialised, being developed to fit the needs of the method used in the Kiruna and Gällivare mines. The ore trains themselves, again, were/are amongst the heaviest in normal service in Europe. The power supply from the Porjus dam was controlled on the basis that the power generated by the regenerative braking used on the descent of the heavily-loaded ore trains to sea level was enough to power the unloaded train the majority of the return journey into the mountains.

The point of all this for this thread is that in 1940, the Swedes had a railway system designed and engineered very well indeed to do one job and one job only. There seems to have been very little link between the Malmbanen and the other Swedish lines. This means that any sudden increase in the load on the line would be very difficult to engineer. First you would have to build a very well-engineered track, fit to take very heavy trains and with passing loops to permit free flow of outward and return trips, then you would have to upgrade the very high-voltage power supply to suit, AND you would have to build a much-greater-than-normal park of locomotives and rolling stock (and, of course, train the crews to man them).

Given that the Swedish economy suffered badly from the restrictions in international trade caused by the War, the Swedes would not have wanted to pay for this work. The Germans might have, but it seems unlikely that work paid for by Germany would have been carried out without German on-site supervision - and, even if this had been permitted by the Swedes, it would surely have resulted in complaints and additional pressure on Sweden from the Allies. As sol pointed out, the window of opportunity was very small, and, in the event, the thing was simply judged to be too much time and trouble.

One thing that hasn't been mentioned so far is how did the Germans pay for the iron ore they took? If they paid in gold or similar hard currency (which seems highly unlikely), then that might be an incentive for the Swedes to upgrade their infrastructure to cope with German demand. If, on the other hand, they were paying by some form of credit (i.e., never-never) system, which meant that the seller had to have considerable faith in the future of Nazi Germany, then where is the incentive for the Swedes?

Update: I've just been reading this Wikipedia article, which mentions German payments of gold bullion, food, and coal. Seems the Germans knew how much they needed Swedish iron ore . . .:

Sweden during World War II - Wikipedia

 

Thank you very much for such a professional explanation. Thank you also to others who have explained the substance of the issue here. I think it's now possible to understand things much better

 

The iron ore gave Swedes some leverage on their negotiations with Germans, e.g. Germany sold DB 605B license rights to Svenska Flygmotor in 1941, but did not sell DB 605A or BMW 801 licenses to Finland even if we had an important nickel mine in Petsamo and extensive military co-operation with Germany.

 

From reading around the subject today, it seems that the main form of payment was coal of which Germany had an abundance from its various conquests and of which the Swedes has, as you pointed out, a shortage. Not much gold seems to have changed hands.

 

There is probably not a single neighbor of Russia from whom they have not taken some territory. And they have not had enough. Ukraine is the latest example of this. It is a good thing that Finland and Sweden are now NATO members.

 

There has been a long running thread on the war in the Ukraine, where this post would sit far better; just be wary this forum tries to avoid too much politics. See: Ukraine War. 2022-

 

Okay, I got it.
I just think there's more politics in your avatar than in my mention of historical facts
Maybe it's more off-topic and that's it

 

Exports of iron ore from Norway and Sweden was to some extent contained by the numerous Bomber Command mining areas covering Danish waters and the Baltic and its coast with Germany. There was only one mining area, code named Bottle off the Norwegian coast. Oslo Fiord was boxed in by the mining areas, coded, Onions and Tomato.

It must have taken continuous Kreigsmarine resources to mine sweep these areas

 

Everything has become much clearer. I just have one more question. It is about the Bergslagen mines and the port of Oxelösund. Was the amount of ore extracted from these mines insufficient for Germany's needs? Or was the railway capacity to the port simply too low? Because if the problem is just the railway, then the distance here is not that great compared with the distance from the northern mines. So maybe it would have been enough to work on this site.

 

This USGS report from 1921 might help.
https://pubs.usgs.gov/bul/0706/report.pdf

Page 99 of the .pdf onwards covers Sweden.

According to this the largest iron ore reserves in Europe lay in northern Sweden and was of very high quality (62% iron). I’m not a geologist but it seems that the further south you go in Sweden the amount of Phosphorus and Titanium in the ore increased making it less suitable for iron ore production.

Somewhere amongst the pieces I read, iron ore production in the south represented only a relatively small part of total Swedish production. Usual story. Now I can’t find it!

 

Thank you, Ewen Scott, for the in-depth explanation. Well, then it's clear that the "eastern route" was practically impossible as a main route only because of the technical difficulties involved.

 

From Eichholtz Volume III 1943-1945, on the German war economy:
From 1939 to March 1940, 2,112,000 tons of iron ore were shipped via Narvik. This was a substantial 1,570,000 tons less than a year earlier.

On ore shipments from January 1942 to October 1943:
From Sweden, i.e., via the Baltic Sea, 8,481,500 t were shipped in 1942.
Via Norway, there were only 541,400 t.

In 1943, there were 8,783,700 t via Swedish ports and only 278,100 t via Norway.

Completely contrary to this are the situation estimates of the Kriegsmarine. Numerous forecasts were made there that turned out to be unrealistic (e.g., the pre-war estimate in 1938 that 4.25 million tons of ore p.a. would have to be routed via Narvik to maintain wartime capability).
The real impulse for the Norwegian campaign was not the ore transports, but the approach of the Reichsmarine not to fight the next war against Great Britain again with a restricted base of operations in the "Wet Triangle" North Sea: The first ideas for this came from 1927/28, and the Norwegian campaign in 1939 was primarily Raeder's impetus.

The legend that Narvik was indispensable for German ore imports, which can still be found in the literature today, was probably invented to make the campaign more palatable to a certain corporal with a pronounced "down-to-earth" attitude.

 

Only as a supplement:

The importance of the Swedish iron ore supplies is usually overestimated. With the Western campaign in 1940, the ore mines of the Minette area fell into German hands. The ore from these mines covered 40% to 43% of German ore requirements.

Swedish imports:
1940: 39,5%
1941: 26,9%
1942: 23,2%
1943: 27,5%
1944: 23,9%

(But: the different ore content and smelting conditions meant an overall increase in smelting capacity with the more suitable Swedish ore. Or to put it another way: if the limited German smelting capacities in 1939/44 had been fed only with Minette ores, crude steel production would have been 15 - 20% lower than if Swedish ores could have been used).

On the other hand, it is underestimated that certain wartime raw materials for Germany, in particular steel refiners such as nickel and molybdenum (for ferro-alloys), were only available via Scandinavia. The largest molybdenum mine in Europe was located in southern Norway. Nickel was mined in Petsamo (northern Finland) and brought to southern Norway by sea.
(The sea link certainly worked, but had to be secured, which tied up considerable naval forces).

On the German side, there were plans for alternative transport routes. Some of the railroad construction projects were pure wishful thinking, especially the Nordlandbahn from Grong to Narvik. For this, the Reichsstraße 50 was built - under horrible circumstances by forced laborers - as far as Lakselv. (In October 1944, many of these constructions were destroyed again)

 

Very interesting. So it was just a legend to appease Hitler?
And Narvik was not really needed?
You say that exports via the Baltic Sea were higher than via Narvik. OK, but if the Nazis had not occupied Norway, it would have been controlled by the Allies (like Iceland later). And then they would certainly not have allowed the Nazis to freely ship iron ore, Finnish nickel or anything else across the Baltic Sea. They would probably even have taken control of Kiruna and Gällivare. This should have been clear even to Hitler, even if he had not been the brightest..

 

The points you make are valid and have influenced the decision-making process, there is no question about that.
In a contribution to a thread, I am unfortunately forced to break such a complex topic down to a few points:
Weserübung was essentially shaped by the Kriegsmarine and its desire for a favorable strategic base for the high seas war against GB. That is why the Admiralty was particularly involved here , which was reflected especially in the considerable losses during the operation.
Of course, other factors also played a role, but it was the Kriegsmarine and its ideas that had the decisive influence.