Here are some examples of subject headings that you can use to locate research on your topic:
Japan -- History -- 1185-1600
Japan -- History -- Tokugawa period, 1600-1868
Japan -- History, Military -- To 1868.
Japan -- social life and customs -- 1600-1868
Military art and science -- Japan
Women -- Japan -- History.
You may still want to consult print indexes from time to time. Here is one that provides coverage you won't find online.
Cumulative Bibliography of Asian Studies, 1941-1965. Subject Bibliography.
Cumulative Bibliography of Asian Studies, 1966-1970. Subject Bibliography.
UM DuBois (21st floor) Z3001.B5