Sweden, following its long-standing policy of neutrality since the Napoleonic Wars, remained neutral throughout World War I between 28 July 1914 and 11 November 1918. However, this neutrality was not maintained without difficulty and Sweden at various times sympathised with different parties 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,