War Council (Civ3)/Civilopedia

Japanese government after the 12th century C.E. was a strange hybrid of
military and civil institutions. "Shogun" was simply the highest
possible military rank, not an imperial title, but shoguns usually ran
an entire government infrastructure entirely separate from the imperial
government (which usually deferred, since the shoguns by definition had
army support). War councils, when they convened, usually resulted in the
reinforcement of existing shogunates or the establishment of new ones.
Since Japan still relied on feudal institutions, army support depended
on vassal support, and this required shoguns to maintain iron control
over their subordinate lords.