Ninja were actually local clans and local samurai called Iga-shu and Koka-shu. In the absence of powerful feudal lords in the warring states period, they independently governed themselves and cooperated with each other to protect the region. Even after their self-governing units declined, their techniques of ninjutsu were valued by the feudal lords they served. Ninja played an active role serving their feudal lords throughout the warring states period.