Sweden, following its long-standing policy of neutrality in place since the end of the Napoleonic Wars, remained neutral throughout World War I from 28 July 1914 to 11 November 1918. However, maintaining this neutrality was challenging, and at different times, Sweden expressed sympathy towards various parties involved in the conflict.
Despite strong pro-German sentiment both in the Swedish nobility and in Swedish political circles, Sweden did not enter the war on the German side. Instead, Sweden retained armed neutrality and continued to trade with both the Entente Powers and the Central Powers. Swedish trade with Germany, particularly in iron ore, eventually led to exports of food to Sweden being greatly reduced, especially after America's entry into the war in 1917. The resulting food shortages, and public unrest in the form of hunger marches and riots, caused the downfall of Sweden's conservative government which was replaced eventually by a social democrat one, bringing about an era of political reform in Sweden.
Sweden intervened militarily in Åland after the collapse of Russia into civil war and the advent of Finnish independence in 1918 and briefly occupied the islands, which Sweden had long sought to acquire because of a large Swedish population that supported annexation, but which were also claimed by Finland. However Sweden ultimately withdrew following Finnish protests. Significant numbers of Swedes also took part as volunteers in the Finnish Civil War, with the 350-strong Swedish brigade playing a role in the decisive Battle of Tampere.
At the end of the war, Sweden was not a signatory of the Treaty of Versailles, which brought the conflict to a conclusion, but Sweden joined the League of Nations, which was formed as a result of the treaty and so it was bound by its restriction of German rearmament. However, Swedish firms provided assistance to their German counterparts that helped them avoid the restrictions of the treaty.
Immediate prewar period German sympathies During the early years of the 20th century the sympathies of the Swedish monarch, and of the Swedish military, were believed to be with the Germans due to cultural links and a shared fear of Imperial Russia. According to the Austrian ambassador to the Ottoman Empire, in 1904, during the Russo-Japanese War, Swedish King Oscar II had proposed an offensive military alliance with the Ottoman Empire against Russia, which was in a difficult military situation. Oscar's successor, King Gustaf V was married to a German, Victoria of Baden, a first cousin of Kaiser Wilhelm II, and the Swedish Marshal of the Realm, Ludvig Douglas, was also known to be a strong proponent of an alliance with Germany. In November 1910, the general staffs of Germany and Sweden had even met in secret to discuss a joint offensive against Saint Petersburg, but the meeting ended without a binding agreement being reached.
While as the royalty of Sweden sympathised with Germany, a number of Sweden's social-democratic politicians were also favourably inclined towards Germany because of their positive view of Germany's social security system and its industrial and scientific achievements. Prominent pro-Germans in the ranks of the Social Democrats included Otto Jarte and Yngve Larsson, both of whom were expelled from the Swedish Social Democratic Party in 1915 for contributing to a book that urged "courageously lining up on Germany's side".
Rearmament crisis
Rearmament was a special concern in Sweden because of the growing tensions in Europe. When Karl Staaff's government proposed a reduction in military spending and the cancellation of the order for the coastal defence ships that were later known as the , more than 30,000 Swedish farmers marched to Stockholm to protest in the Peasant armament support march. In response, King Gustaf gave a speech written by the ardently pro-German explorer Sven Hedin in the courtyard of the Royal Palace in Stockholm that argued for higher military spending.
The speech prompted a constitutional crisis in Sweden (the so-called "Courtyard Crisis") because of the interference of the crown in the running of the state, as the constitutional monarchy was supposed to be neutral in partisan politics. When King Gustaf refused to tone down his rhetoric on the subject of defence spending, Karl Staaff's government resigned and was replaced by the conservative government of Hjalmar Hammarskjöld.
Early war period
July Crisis During the July Crisis, both King Gustaf and Knut Wallenberg, the Swedish foreign minister, gave assurances to the Central Powers that in a war between Germany and Russia, Sweden would never stand on Russia's side, and that although Sweden would issue a declaration of neutrality at the start of the conflict she would retain the freedom to take other action later. The assurances given by King Gustaf and Knut Wallenberg led the German secretary of the foreign ministry, Gottlieb von Jagow, to believe that Germany would be supported by Sweden in the upcoming conflict. Talks even took place between the military and naval staffs of Sweden and Germany on cooperation, and preliminary arrangements were made for Germany to use bases and anchorages on the east coast of Sweden and on the island of Gotland.
Wallenberg also warned the Germans that Sweden could not intervene too soon as this might prompt a British intervention in the conflict, although this in turn led the German minister in Stockholm, Franz von Reichenau, to suggest that if Britain entered the conflict Germany should issue an ultimatum demanding that Sweden join the war. At the same time messages were sent by the Swedish foreign ministry to Russia promising that Sweden would remain neutral, although troops were sent to watch Sweden's frontier with Russian-ruled Finland.
Declarations of neutrality
Sweden declared neutrality in the Austro-Serbian conflict on 31 July 1914, and in the general conflict of Germany against France and Russia on 3 August. Both declarations left open the possibility that Sweden might later change her position if other countries joined the conflict. On 2 August, however, Wallenberg, speaking to the British minister in Stockholm, had repeated his assertion that if Sweden were driven into the war, she would never fight on the side of Russia. Apparently fearful that Germany might issue an ultimatum demanding Sweden choose sides (something the German Kaiser had threatened to do during a visit by King Gustaf to Germany in 1913) Wallenberg also promised Franz von Reichenau that Swedish neutrality would be "benevolent" to Germany.
The position of Norway also concerned Wallenberg, as he believed that the Norwegians would prefer to intervene on the British side if they entered the war. On 8 August the two countries (Sweden and Norway) issued a joint declaration of neutrality warning that they would maintain their neutrality against all belligerents and would guarantee each other's neutrality. A further joint declaration was made by the three kings of Denmark, Norway, and Sweden on 18 December 1914, and the Swedish army units that had been sent to the Finnish border were stood down.
Germany offers an alliance In early 1915, Arthur Zimmermann, the Under-Secretary of State at the German foreign ministry, approached Hammarskjöld, who was on a visit to Berlin, with an offer of potentially forming a "Nordic Block" under Swedish leadership in return for an alliance between Sweden and Germany. Whilst Hammarskjöld rebuffed this first offer, Zimmermann persisted and approached Ludvig Douglas with an offer for a renewed Swedish Empire covering Finland and the Baltic provinces of the Russian Empire. Douglas then conveyed this offer to King Gustaf on 8 June 1915, and also to Hammarskjöld and Wallenberg, however only King Gustaf received it positively.
Following this failure, Prince Maximilian of Baden, a cousin of the Swedish Queen Victoria, made a further overture to King Gustaf. Prince Max had been instructed by Kaiser Wilhelm II and Erich von Falkenhayn, who wished to integrate Sweden into the German Mitteleuropa, to obtain an alliance with a view to a joint attack on St. Petersburg, in return Germany was willing to offer material and military support as well as the promise of Åland (which contained a Swedish-speaking population, and the fortification of which by the Russians during 1915 caused concern in Sweden), an adjustment of the frontier, and an independent or autonomous Finland. King Gustaf rejected this offer on 20 November 1915 as, without a clear casus belli, he could not be sure of popular support for the war.
On 1 December 1915 two leading pro-German Swedish political figures, the Social Democrat Otto Järte, and the conservative editor Adrian Molin, had an audience with King Gustaf in which they urged him to join the war on Germany's side. They urged him to consider that "If the Entente wins, ideas of republicanism and parliamentarism will win the ratification of world history". According to Otto Järte's account, the King stated repeatedly that he was of the same view and that Sweden would "speed into action" once German forces had entered Finland; however, according to Järte the King also stated that as a constitutional monarch he could not make any binding promises.
Whilst talk of an alliance eventually came to nothing, Sweden did favour Germany over Russia in at least one important respect. Knut Wallenberg, without the knowledge of Hammarskjöld, allowed the Germans to use Swedish ciphers to communicate with their embassies overseas, and these communications were carried over the telegraph cables used by Sweden to communicate with their embassies. This allowed the Germans to communicate with their embassies via Stockholm without their communications being so easily censored and intercepted by the British. Despite claiming that they would end the practice in late 1915, a scandal erupted in 1917 when it became known that a telegram from the German chargé d'affaires in Argentina, Count Luxburg, to Berlin proposing that certain Argentine ships be "sunk without trace" had been transmitted via the facilities of the Swedish foreign ministry. This became known as the "Luxburg Affair".
Swedish exports to Germany increased massively after the war started, with exports for the two months December 1914 to January 1915 being eight times that of December 1913 to January 1914. This great increase in exports helped Germany mitigate the effect of the stringent Allied blockade on German trade.
Swedish military preparedness during the war Army During the entirety of the war, the active strength of the Swedish army never exceeded 13,000 men, even after the doubling in strength requested in Hammarskjöld's Army Bill of 1914 of reserve formations from six to twelve infantry divisions and a cavalry division. As the war went on and the threat of invasion receded, the number of active, deployable men, by 1918, had fallen as low as 2,000.
While relatively well equipped by the standards of 1914, as the war went on this force was less and less well prepared for fighting a conflict according to the prevailing standards of the day. For example, in 1914 the number of machine guns in a Swedish army division's establishment (24) was roughly the same as that of a division of the German or French army, however by 1918 French army divisions had 108 heavy and 405 light machine guns, whilst German army divisions had 108 heavy and 216 light machine guns, a Swedish army division still had 24. The situation with field artillery was similar: in both 1914 and 1918 the average Swedish infantry battalion was supported by 3.6 field guns, a figure similar to that of the great powers in 1914, yet by 1918 the equivalent figure for a German battalion was 8.4 and for a French battalion was 12.