Battle of Kōnoshima
Date: 8/8 of Eiroku 9 (1566)
Location: Kōnoshima near the Kiso River in Mino Province on the border with Owari Province
Outcome: The Oda and Saitō armies were temporarily stranded by flooding, and when the Oda forces attempted to retreat, some drowned while others were killed along the river by Saitō forces.
The Battle of Kōnoshima occurred on 8/8 of Eiroku 9 (1566) and was waged between Oda Nobunaga and Saitō Tatsuoki. Historical records in regard to this battle are scarce so the actual events are not well understood.
The death of Saitō Dōsan caused a break in the alliance between the Oda of Owari Province and the Saitō of Mino Province, after which Oda Nobunaga attempted a series of incursions into Mino.
On 7/29 of 1566, the Oda army marched to the border with Mino, but encountered an unexpected flood, and after crossing the Kiso River, went to Kōnoshima. Upon learning of these developments, Saitō Tatsuoki immediately led forces to Kōnoshima, while the Oda pulled back to the riverside and set-up a camp. The Saitō advanced up to the Sakai River for their defense, but, on 7/30, the Kiso River overflowed so neither side could move from their positions. When the flooding finally subsided before dawn on 8/8, the Oda began to withdraw but many soldiers drowned in the river. Meanwhile, the Saitō killed some of the opposition forces along the river. The Oda army abandoned their weapons and scattered in disarray.
A jointly sealed covenant from a retainer of the Saitō is the only historical account of this event. This document is signed by Andō Sadaharu, Hineno Hironari, Takegoshi Naomitsu, and Ujiie Naomoto. The name of the addressing is missing, but Kaisen Jōki, the abbot at the Eirin Temple in Kai Province is believed to have been the intended recipient. Moreover, the document may be viewed as boasting on the part of the Saitō or to poke fun at Nobunaga so the contents should be considered in that light.
Believed to have occurred either in 1564 or 1567, this battle may provide clues to the toppling of Inabayama Castle by Nobunaga. The document is dated 8/18 which, given the sequence of events, would be in 1566. As of 1566, Nobunaga had not yet defeated the Saitō and therefore Inabayama Castle would not yet have been toppled in 1564.