The original purpose was to isolate such dangerous elements, but the government of the time had a policy to protect the north by encouraging reclamation of Hokkaido, in order to be ready for Russia's advancing southward.
本来危険分子の隔離が目的であったが、当時政府はロシアの南下に備える為に北海道の開拓を推し進め北の守りを固める方針をとっていた。