China–German relations were formally established in 1861, when Prussia and the Qing dynasty concluded a Sino-German treaty during the Eulenburg expedition. A decade later, the German Empire was established, with the new state inheriting the Prussian-era treaties concluded with China. Sino-German relations during the late 19th and early 20th century were frequently tense, as Germany followed the example of other European colonial powers in carving out a sphere of influence in China; by 1914, Germany had obtained several concessions in China, including the treaty ports of Yantai and Qingdao and most prominently the Jiaozhou Bay Leased Territory. Germany was a member of the Eight-Nation Alliance, and the Imperial German Army participated in the suppression of the Boxer Rebellion. After World War I, during which Germany lost all its territories in China, Sino-German relations gradually improved as German military advisers assisted the Kuomintang government's National Revolutionary Army, though this would change during the 1930s as Adolf Hitler gradually allied himself with Japan. During the aftermath of World War II, Germany was divided in two states: a liberal and democratic West Germany and a communist East Germany. Cold War tensions led to a West German alliance with the United States against communism and thus allied against the People's Republic of China (PRC). The Eastern part was allied through the Soviet Union with the PRC. After German reunification, relations between Germany and China have gradually and vastly improved. History Early contacts Unlike Portugal or the Netherlands, German states were not involved, on the state level, in the early (16-17th centuries) contacts between Europe and China. Nonetheless, a number of individual Germans reached China at that time, in particular as Jesuit missionaries. Some of them played a significant role in China's history, as did Johann Adam Schall von Bell (in China in 1619–1666), who was in Beijing when it was taken by the Manchus in 1644, and soon became a trusted counselor of the early Qing leaders. Meanwhile, in Rome another German Jesuit, Athanasius Kircher, who never got to go to China himself, used reports of other Jesuits in China to compile China Illustrata, a work that was instrumental in popularizing knowledge about China among the 17th-century European readers. The earliest Sino-German trading occurred overland through Siberia, and was subject to transit taxes by the Russian government. In order to make trading more profitable, German traders took the sea route and the first German