First of all I want to say sorry again for this very, very, very late response. I have been busy with exams, and have just not had the energy to write a long reply. But I'll try now that I have recuperated a bit.
Right I'm wondering how things might have developed if the British had a different attitude with regards to the Danish straights.
Ah, alright.
The problem with an invasion of Denmark at the beginning of World War I was that neither side had troops to spare for another front. The Germans had tied their dearest hopes and desires to the Schlieffen Plan, which called for 7/8ths of the army to be sent to the Western Front and to invade and conquer France quickly. In the early 1900s an invasion of Denmark was still considered a possibility at the onset of a war with Britain. Schlieffen had estimated that two corps would be needed for a conquest of Denmark. However, the army thought tying two corps up with such an invasion a waste, as they were needed in Belgium and France because of the Schlieffen Plan. Only the German Navy was keen on an invasion of Denmark, and the German Navy lost the battle over whether to invade Denmark or not in 1905, when the Entente Cordiale was concluded. This victory was further cemented by I. C. Christensen secret negotiations with Moltke the Younger, where he made it clear that Denmark would never join a war on the side of Germany's enemies.
However, the German Navy had actually convinced the Kaiser that Denmark should be invaded in case of war in 1904. This was because it was feared that the Russo-Japanese War would escalate, and that the Royal Navy would sail through the Belts and into the Baltic. The Navy continued to want an invasion of Denmark, and Adm. von Holtzendorff still argued in 1912 that the High Seas Fleet should be sent into the Baltic and Kattegat against Denmark and Norway, but this was seen as heresy against Tirpitz's established doctrine of sending the High Seas Fleet into the North Sea. Holtzendorff was therefore retired in 1913. On the British side, Fisher's Baltic Project is well-known. Prior to Gallipoli Churchill also at first proposed an expedition into the Baltic in November 1914 (if I recall correctly) to break the deadlock on the Western Front. The problem with changing the British attitude towards Denmark at the onset of the war is that it would require Britain not to have made the treaties with and promises to France that it had done. Britain can't spare divisions for both Denmark and France in August 1914. If there weren't any such treaties and promises between Britain and France you're essentially looking at a completely different war, perhaps even a war without initial British involvement. The British might possibly have adopted a different attitude that would violate Danish neutrality at the onset of war without infringing on any existing treaties with France, but then it wouldn't have involved land forces but only the Royal Navy. This is also why the British Army isn't involved in any of the planning for operations in the Baltic before the start of the war. One obvious policy that could draw in Denmark would be a close naval blockade.
Danish historian Michael Clemmesen has also written about the possible implications for Denmark of a close British naval blockade. You can read that here:
http://www.clemmesen.org/articles/Royal_Navy_Strategy_Discourse.pdf
There is a lot in this article which I think you will find interesting for the prospect of a British invasion of Denmark. As you can see on page 11 and 27, Britain considered occupying Horns Rev and Læssøe. Those two islands controlled strategic positions close to the German coast and in the entrance into the Baltic respectively. I think an occupation of Anholt would've been likely as well in such a case. Esbjerg was also thought of as a possible landing spot, but is probably too close to the German border, and it would therefore require an army corps. But as he also writes, the British also presumed that the Danish would join the Allies and that the Germans would invade beforehand when the Royal Navy appeared in the Kattegat. There is, however, a problem with this presumption that I will come back to a bit further down.
As for how Denmark would react to all this, two Danish naval officers made these assessments at the time:
First Lieutenant Henri L. E. Wenck 1900 (in 1914 he was a Captain)
:
The biggest threat to Denmark is a surprise coup-attack on Copenhagen. Such an attack would take place before mobilisation has begun or is finished, and would have the objective of capturing the entire Danish state apparatus and forcing Denmark to join the war on the side of the attacking great power. Wenck concluded that only Germany would be able to execute such an attack, and that Germany would be able to do so with only a small force. Wenck mentioned three possibilities for how such an attack might proceed:
- An enemy naval force sails into Copenhagen's inner harbour without taking hostile action and delivers an ultimatum demanding either surrender or an alliance. The ultimatum will make it clear that any mobilisation will be seen as a casus belli. Wenck says such an attack has the weakness that Copenhagen's fortresses can contend with the German force.
- An enemy combined operations force makes a surprise attack on Copenhagen and the Zealand naval fortresses. Wenck says such an attack has the weakness that the fortresses will try to resist the force.
- An enemy forces makes a surprise coup attack on Copenhagen and lands troops in Copenhagen's inner harbour, occupies all government buildings, depots, arsenals and barracks quickly. Copenhagen is taken and Denmark is therefore completely defeated since the country falls with the capital, and all of the country's depots are in Copenhagen and the entire defense plan and mobilisation plan centers around Copenhagen. Wenck can see no weakness in such a move by an hostile force, and concludes that it will succeed. He says that such an attack might not be likely by a normal enemy, who would such an operation daring or brash, but also says that Germans are certainly willing to take big risks if they know they can win a big prize.
Wenck considered this last possibility the biggest danger, and kept talking about the dangers of it. He reiterated his position in 1913, and it was also essentially this last operation that took place on the 9th of April 1940. Wenck proposed many measures to guard against such an attack, but he also agreed with Adm. Kofoed-Hansen that Denmark's only way of survival if it got involved in a European war would be in an alliance with Germany. The purpose of the Danish Navy would be to guard the entrance into the Baltic against the Royal Navy.
Another Admiral, Thomas V. Garde, added that the British might see necessary to occupy Iceland and the Faroe Islands.
Captain Victor L. Lorck 1912:
Lorck disagreed with Kofoed-Hansen and instead sympathised with the very pro-English army leadership, and he also made a timeline analysis of how Denmark might be drawn into a big European war. However, here I will only surmise his evaluation of how Denmark will choose side:
- The Danish government's relationship with Germany in the period leading up to the war.
- The possibility of a referendum that see the government replaced by an anti-German one, or the possibility of an anti-German coup d'état.
- The views of the Danish Army and the Danish Navy.
Was the mining of the Great Belt done exclusively by Danish ships?
This link describes that the Germans began mining the Great Belt on August 5th, followed by an ultimatum to the Danes telling them to follow suit. The Danes acquiesced, but it seems like there was some confusion even among the Danes about the status of those minefields, what with the kings telling each other they weren't armed. It's not even clear to me that the British knew there were German minefields involved. If there had been a Royal Navy destroyer flotilla or cruiser squadron lurking in Denmark's seas on August 5th providing the British government more accurate intelligence, I assume the mining of Danish waters would be much more contentious, and possibly have resulted in German attempts at occupying Denmark. Alternatively, (if the British had a pre-war plan to launch an offensive into the Baltic) a Royal Navy fleet might sail straight into a Danish minefield they thought was unarmed.
Yes, the German started mining the Great Belt, and the Danish Navy then coalesced. However, though a British naval squadron in the region might mean some skirmishes between Germany and Britain, and would put some pressure on Denmark, a German invasion of Denmark in August 1914 is very unlikely. This is where I come to the aforementioned problem with the British presumption of a German invasion of Denmark, which I mentioned further up.
The German Army did not have troops to spare for an invasion of Denmark. IX Reserve Corps was kept in Schleswig in the opening days of the war to respond to a possible British invasion, but it wouldn't have been enough to invade. The Germans might possibly have considered occupying Esbjerg, but only if the British had already landed. Neither side had the divisions required to launch an invasion and maintain an occupation of Denmark in August 1914. The Schlieffen Plan dictated German planning towards Denmark as I mentioned above, and it wasn't until 1916 that the Germans would begin drawing up plans for an attack on Denmark again. This isn't to say that the Germans couldn't have been made to attack Denmark, though. I think a coup attack like Wenck described would be the most likely course of attack if the Germans are forced to act by a British squadron in the Belts. Such an attack might very well succeed in forcing Denmark to join Germany's side, and the British would subsequently occupy Iceland, the Faroes, Læssøe, Anholt and maybe Horns Rev. The Baltic Project might then have been executed in late 1914 or early 1915, which would mean a proper invasion of Denmark. Churchill and Fisher would probably bet on King Christian and the Danish Army couping the government and switching sides in the event of such an operation. Nevertheless, the Danish Navy might still be drawn into combat against the Royal Navy due to the strong personality and realpolitical convictions of Adm. Kofoed-Hansen.
I think the British would probably land on Sjælland. An initial landing in Jylland would be too close to Germany, though they could probably also land on Vendsyssel with success and win the big strategic victory of capturing Frederikshavn.
Do you think Denmark would have joined the British regardless of the circumstances? I mean I would think it's one thing if Germany invades Jutland because there's a British squadron coaling in Aarhus, and it's another if a British troop convoys shows up demanding the keys to Copenhagen's fortifications; at least I assume so. Also, do you have any idea what level of Royal Navy activity in the Kategatt in 1914 would have prompted Germany to invade?
No, Denmark could've been forced to join the Germans. However, I also think Denmark would've switched sides to join the British given the opportunity.
The policy of the government, the Navy and Venstre were that Denmark should never join the war on the side of Germany's enemies. I. C. Christensen even proposed an alliance in return for Northern Schleswig during his secret talks with Moltke. However, the King, the Army and most of the population had a strong anti-German sentiment, and would've been against Denmark fighting on the side of Germany. The King did, however, realise that fighting Germany probably would mean the end of Denmark, and made assurances to the Kaiser that Denmark wouldn't join on the side of Germany's enemies. Such an assurance doesn't mean that he doesn't want Denmark to fight Germany if forced, though.
Denmark is an extremely centralised country. It probably rivals France for the top spot in Europe. Everything revolves around Copenhagen. A British squadron demanding the keys to Copenhagen and forcing Denmark to pick sides would ironically make Denmark join the British, since that means that the British have control of the Baltic, and the Germans therefore can't threaten Copenhagen. This also gives the King and the army leadership a free hand to pursue a pro-British line (though both would prefer neutrality, if perhaps a pro-British neutrality, if possible. The King very much wanted Denmark to be kept out of the war, and every day throughout the war he thanked God in his diary for "the peace which he has granted our country". If forced, he would fight, though). However, as Wenck says, such an operation is unlikely, and only the Germans would be able to pull off a coup attack on Copenhagen. A German coup attack could mean that Denmark would be forced to join the German side, as Denmark falls if Copenhagen falls.
I think that the Germans could feel forced to make a move on Denmark, but they didn't have the ressources for such an operation in August 1914. Clemmesen writes that the German ultimatum given to Denmark about the mining of the Belts was a bluff and that there wasn't any force behind it, but that the Danish didn't realise this. As such, the Germans might possibly be able to execute another more daring bluff, and make a surprise attack on Copenhagen to force Denmark to join Germany's side. So yes, I think you might have your scenario for an invasion in 1914 here: the British adopt a different attitude towards the Baltic prior to the war, meaning that Wilhelm II also allows the German Navy to go through with a surprise coup landing in Copenhagen, forcing Denmark to join the side of Germany. Meanwhile the British occupy the small but strategically important Danish islands in the Kattegat and Denmark's colonies in the Atlantic. Denmark would be a very reluctant ally, however, especially since the hundreds of years old animosities have just been reinforced by a new German act of aggression, and Denmark would most likely keep all of her forces at home to guard against a possible landing operation, while also strengthening the navy. I think Denmark would switch sides if the British make a Gallipoli in the Baltic and land on Sjælland.