Linked from
The 40 pages that link to Russian conquest of Siberia, each with the reason it gives.
Treaty of AigunNarrower topic: Its eastward advance brought Russian forces to the Amur frontier.
YakutskNarrower topic: Yakutsk began as a fortified outpost within this eastward expansion.
Semyon DezhnevNarrower topic: Dezhnev's expeditions extended this expansion into the far northeast.
IrkutskNarrower topic: Irkutsk emerged as Russia extended its power eastward across Siberia.