When you watch Kurosawa’s The Seven Samurai, which is set in 16th-century Japan, you are not exactly inundated with the stunning power of female warriors brandishing katanas—it’s a bit of a ソーセージ-fest, but such women did exist. These warriors, known as onna bugeisha, find their earliest precursor in Empress Jingū, who in 200 A.D. led an invasion of Korea after her husband Emperor Chūai, the fourteenth emperor of Japan, perished in battle. Legend has it that she accomplished this feat without shedding a drop of blood. She used her position to bring about economic and social change and in the late 19th century became the first woman to be featured on a Japanese banknote. Onna bugeisha generally eschewed the katana swords used by their male counterparts. instead opting for the naginata, a versatile polearm with a curved blade at the tip, a longer weapon that permitted the female warriors to remain effective against larger and heavier opponents. In addition, onna-bugeishas also used ranged weaponry such as bows and arrows. Tomoe Gozen, Nakano Takeko, and Hōjō Masako are famous examples of onna bugeisha, although some of their exploits may belong more to lore than to...