The work that follows is about three things: a geographical region, an historical episode involving this region, and an underlying enigma. The region in question is a massive chunk of territory at the southeastern-most extremity of the Russian landmass, where the Siberian frontier presses eastward to the Pacific ocean and south into Manchuria. The dominating natural feature of this area is the mighty Amur river. The Amur has its origins at the confluence of the Shilka and Argun rivers east of Lake Baikal and flows on for some 1,800 miles to empty into the Tatar straits opposite the northern tip of Sakhalin. With numerous tributaries feeding it from the north and south, the river commands a drainage basin of nearly three-quarters of a million square miles. It was not however this vast natural–geographical zone in its entirety that the Russians in the nineteenth century had in mind when they spoke variously about the amurskii krai, amurskaia oblast', or priamur'e, and nor is it the scene of this study. The specifics varied considerably, as we will see, but for the most part they were referring to the river itself and the lands immediately along its northern bank. At a relatively late point, the Ussuri river – a major tributary which feeds into the Amur from the south – was included in this designation as well, along with all of the territory from the Ussuri east to the coast of the Tatar straits.