But Danish nationalist forces have always insisted that Schleswig must implement a Danish constitution, not for the sake of land expansion, Denmark is a small country with a small population and no ambitions for expansion. However, the main inhabitants of Schleswig were Danes, and they could not give up. What they seek is to establish a modern Danish state on the land inhabited by the Danes, so that the Schleswig, where the Danes live, must become a state using the same constitution as the Kingdom of Denmark.

The problem was that the Danes did not care about the principality of Herstein, which was inhabited by the southern Germans and ruled by their king, and did not seek to enact the Danish constitution throughout the country ruled by the Danish king. However, the Germans of Herstein could not accept the annexation of Schleswig, which was partially inhabited by Germans, to Denmark.

Although the Grand Duke of Herstein was the king of Denmark, they had always identified themselves and were recognized as a German state, and although they did not join the German Empire, they joined the North German Customs Union.

The most important thing is that Herstein has an inseparable agreement with Schleswig. Denmark's attempt to impose a Danish constitution in Schleswig was perceived by the Germans of the two principalities as a breach of the agreement.

There had always been separatist sentiments in the two principalities, and not only the Duchy of Herstein, which was inhabited entirely by Germans, but also the small number of German residents in Schleswig, were reluctant to join Denmark, hoping to break away from Danish control and join the Greater German region.

However, under the principle of succession prevailing in Europe, they did not object to the fact that the King of Denmark was also their Grand Duke. That is, they wanted their country to join Germany, and then a state was formed in which the Danish king was a king in Denmark, but in Germany he was an archduke under the name of the German emperor.

The Germans in the two principalities opposed the Danish constitution, and the Danish forces imposed it, which led to two Prussian-Danish wars. But there was only one such controversy in this history, and that was in 1846, in the context of the European Revolution, when Denmark tried to annex Schleswig, turning the Danish-majority principality into Danish territory and part of the Kingdom of Denmark, rather than an independent principality. But Herstein in the south was opposed, and in the end Prussia supported Herstein, and the army marched here, and the Danish army marched into Schleswig. However, because of the revolutionary atmosphere at that time, coupled with British pressure, Prussia withdrew from the area. The two sides signed the London Protocol to maintain the status quo.

Later, Christian IX succeeded to the throne, and the new king, under the oppression of domestic political forces, had to announce the implementation of a new constitution, and consulted Germany on the question of whether to implement it in Schleswig, and Bismarck opposed it. Historically, Denmark introduced laws under Bismarck's opposition, which resulted in the Prussian-Danish War. But in this history, due to the early unification of Germany and its emergence as the first power in Europe, the Danish king and Danish political forces did not dare to insist on the forcible extension of the constitution to the Duchy of Schleswig, under the opposition of Bismarck. Thus this legal issue has been preserved, but the contradiction has also been preserved.

Herstein in the south was a member of the North German Confederation and a member of the German Customs Union, but it did not become a member of Germany after the reunification of Germany like other German states, but because of the King of Denmark, he has always maintained the status of an independent principality, so the German nationalists have always been dissatisfied and have always wanted to join Germany.

After reunification, Germany also hoped to unify the last of the states inhabited by German residents into Germany. It was only during Bismarck's reign that he had been avoiding causing Germany to cause dissatisfaction among the foreign powers, so he did not take action against these two small states, otherwise Denmark would not have been able to resist Germany's iron hooves. Although Denmark repeatedly expressed its willingness to give up Herstein in exchange for Germany's support for Schleswig's annexation to Denmark, Bismarck did not accept it, because accepting this condition would cause dissatisfaction among the Hersteinians. Bismarck had to give priority to the attitude of the Germans, who preferred not to have a Herstein than a Herstein who was dissatisfied with Germany.

Before the war, Bismarck resigned as chancellor, and then the Franco-German war broke out, and Denmark hoped to use this opportunity to solve the Schleswig question.

But the German emperor also refused to negotiate on this issue.

This made Denmark more and more dissatisfied, and in recent years, the relationship between the Scandinavian countries in Northern Europe is very close, the personal relationship between the Danish king and the former Swedish king is very close, the Swedish king is promoting pan-Scandinavianism, Denmark has even established a monetary alliance with Sweden, issuing a currency with similar gold content. The former king of Sweden also expressed to Denmark that Sweden was willing to protect Denmark in the event of a war with Germany over the Schleswig issue. It's just that this guarantee was abolished by the Swedish parliament.

But the relationship between the two countries is still close, and in the event of war, Sweden will certainly prefer to support Denmark, provided that its own security can be guaranteed.

If Denmark had fought Germany alone, then Sweden would not have dared to guarantee it, but Germany was not only caught in the war with France, but now Britain had entered the war.

The British are not only good at diplomacy, but also have a very close relationship with Northern Europe, in the last one or two decades, although the population of Northern Europe is not large, but the population is small at the same time, the resources are relatively rich, especially Sweden, the mineral resources represented by iron ore are very rich, and high-quality. But their main trade partner is the United Kingdom, and the main foreign investment also comes from the United Kingdom. Britain has more influence on the Nordic countries than any other country. At the same time, Britain may protect their security, at least for now.

Britain also has a tradition of attaching importance to diplomacy, so after Britain entered the war, it immediately seized the contradiction between Denmark and Germany, and actively encouraged Denmark to go to war against Germany. At the same time, Britain persuaded Sweden that it would support Denmark in the event of a war with Germany.

At this time, the Nordic countries were actually Denmark and Sweden, and Norway was united with Sweden at this time, and was ruled by the Swedish king. The combined population of the three countries is more than 8 million people. The military system and equipment level are similar to those of Germany, because Moltke graduated from the Danish Military Academy, and although these countries cannot defeat Germany, it is not because the military system is not good, but mainly because of the small population and lack of troops. But if the three countries are combined, and the British provide equipment, they still have the ability to form an army of nearly one million.

Therefore, it should not be underestimated.

But the three countries did not want to fight, even Denmark, and they did not want to go to war with Germany for territory. Therefore, they first announced the use of the Danish constitution in Schleswig, believing that Germany, which had already fallen into a state of war with Britain and France, would not go to war with Denmark at this time.

If everything is normal, Germany may really take into account the pressure of Britain and France, and will not provoke Denmark at this time, let the Danes succeed, and create an established fact. The problem was that the Hersteins did not agree, and as soon as Denmark announced the introduction of the Danish constitution in Schleswig, the Germans in the southern part of Schleswig rebelled, and the Hersteins decided to support their compatriots, and the Kingdom of Denmark sent troops to suppress the rebellion. Without the intervention of external forces, this would have become a Danish civil war.

However, the Principality of Herstein turned to Germany for help, and the Herstein and Schleswig regions, where millions of people lived, half of whom were Germans, did not dare to give up the demands of these German states, so Germany declared that Denmark had violated the London Agreement and changed the political status of Schleswig. Within 48 hours, Denmark was required to announce the abolition of the new constitution. Denmark refused, and as a result, the Germans marched into Herstein and joined forces with the Duchy of Herstein to counterattack the Danish army.

So the German-Danish War broke out, and after the outbreak of the war, under the joint lobbying of Britain and France, Sweden declared war on Germany on the grounds of Germany's invasion of Denmark, banned the export of iron ore to Germany, and mobilized the army to aid Denmark.

Following Greece and Italy, two more European countries joined the war.

But war continues to be attractive to countries with disputes of all kinds, including territory. Outside, there are other countries pulling in.

Compared with Denmark and Sweden, which are only small countries, Britain, France and Germany cannot ignore those big countries, and the main ones they fight for are those big countries. Among them, the most important ones that cannot be ignored are the Austro-Constitutional Empire and the Russian Empire, one of the five traditional powers of Europe.

Despite the co-optation of both countries, for Britain and France, Austria-Hungary maintained a long-standing friendship with Germany during Bismarck's reign, and Bismarck was able to tolerate some German states that were not under German rule, such as Herstein and Schleswig under the Danish king, and Austria under Austria-Hungary. Therefore, Austria-Hungary had a close relationship with Germany in recent years, and there was no contradiction.

But the grievances of history can not be changed, Germany that was forcibly twisted together by Bismarck is not monolithic, the southern states of Germany, led by the Kingdom of Bavaria, the Kingdom of Baden and the Kingdom of Württemberg, nearly one-third of Germany's land, although living are Germans, but they are Germans who believe in Catholicism, and they are incompatible with Prussia who believes in Protestantism, and even they assassinated Bismarck, Bismarck also used the culture war to fight and suppress Catholicism, and the southern German states have always been dissatisfied with the rule of the German Empire. They were closer to Austria, which was also a Catholic country, and even fought on the side of Austria in the Austro-Prussian War.

Britain and France guaranteed that as long as Austria-Hungary joined the British and French side of the war, they would support the annexation of South Germany to Austria-Hungary after the war, and that Britain and France would not interfere as to whether to directly annex Austria to the Duchy of Austria or to join Austria-Hungary as an independent state. Britain and France also guaranteed that because the Balkan Empire with Greece as the core joined the Sino-German alliance, Austria-Hungary joined the British and French sides, and could also regain the lost Wallachia from the Balkan Empire, and also agreed to the expansion of Austria-Hungary in the Balkans, including the annexation of Albania, which was lost to Greece.

At the same time, of course, Germany promised Austria-Hungary, a fraternal empire, that the benefits they could take from the enemy would also be taken from the enemy. As Italy joined the side of Britain and France, Germany pledged to support Austria-Hungary in regaining its traditional territories that had been taken away by Italy, and the rich northern Italian regions were not limited to Lombardy and Venesia but even more.

In the wooing of Russia, both sides also did everything they could.