China, weakened by the Opium Wars, was forced to give up the left bank of the Amur River to Russia under the treaty of Aigun (1858). The Russian expansion was largely an initiative of Nikolai Muraviev, governor general of East Siberia, and backed by military force. However, the Russian side felt that it needed some moral justification as well. Christianity, progress and civilization were the keywords then dominant among European (incl. Russian) intellectuals and politicians. China was considered a backward Asian empire and its moral right to administer its neglected periphery was doubted. The fact that China’s northern periphery was almost terra incognita for contemporary European scientists served as an example of its underdevelopment. Scholarly exploration of a region still unknown to the European public meant glory for the country and gave a sort of moral right to the ensuing occupation. Richard Maack’s journey to the Amur River valley in 1855-1856 was such an expedition. The paper focuses on its historical background and its reception both in Russia and Europe. Special attention is given to Maack’s relations with native peoples and Chinese provincial authorities. His book Puteshestvie na Amur (Travels to the Amur, 1859) serves as the main source.