The Kōka ikki or Kōka Confederacy, historically known as the Kōka-gun Chūsō, was a military confederation and network of ninja in Kōka District 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" 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 in defeating a punitive expedition by Ashikaga Yoshihisa. In gratitude for their assistance, the Rokkaku granted 21 prominent families from Kōka positions as retainers.