Kōka ikki

The Kōka ikki or Kōka Confederacy, historically known as the Kōka-gun Chūsō, was a military confederation and network of ninja (then known as shinobi) in Kōka District (often spelled Kōga) in Southern Ōmi Province during the Sengoku period of Japan. Kōga-ryū, one of the two major traditions of ninjutsu that survived by fleeing to the mountains, is named after the confederacy and attributes its origins to it. The confederation emerged in the 15th century when local "jizamurai" (government administrators technically of peasant class) formed mutual defense and aid co-operatives. Local co-operatives together formed larger co-operatives, and all together at the district level. The armies of Kōka achieved fame in 1487 in the Battle of Magari, when they assisted the Rokkaku clan (who controlled the portions of Southern Ōmi province immediately to the north) in defeating a punitive expedition by Ashikaga Yoshihisa. In gratitude for their assistance, the Rokkaku granted 21 prominent families from Kōka positions as retainers.

Although they were previously rivals of Iga Province to the south, by the 16th century Kōka formed an alliance with Iga. As Iga also partook in the Battle of Magari, this alliance was established by 1487 at the latest. Kōka also continued its alliance with the Rokkaku. The independence of the confederation ended with the subjugation of Kōka in 1574 to the Oda clan. After that conquest, Kōka ninjas served Tokugawa Ieyasu and then his descendants late into the Edo period.