The earliest Sino-German trade occurred overland through Siberia, and was subject to transit taxes by the Russian government. In order to make trading more profitable, Prussia decided to take the sea route, and the first German merchant ships arrived in Qing China, as part of the Royal Prussian Asian Trading Company of Emden in the 1750s. In 1861, after China's defeat in the Second Opium War, the Treaty of Tientsin was signed, which opened formal commercial relations between various European states, including Prussia, with China.