Sō organizations were local, grassroots groups formed during the Sengoku period in Japan, primarily as a response to the power struggles among daimyō and their feudal armies. These groups played a significant role in promoting community defense, trade, and agricultural production, while also acting as a form of social organization that fostered solidarity among members. They emerged due to the instability of the warring states era, where the need for collective action was vital for survival and prosperity.