What was the Battle of Anegawa?
Anegawa was a river battle in Omi Province between the combined armies of Oda Nobunaga and Tokugawa Ieyasu and those of the Azai and Asakura houses. The Oda–Tokugawa side won the field.
It was not decisive. Both defeated houses survived for three more years, and the wider coalition against Nobunaga — temples, the Takeda, the exiled shogun — kept him fighting on several fronts until 1573.
Why did it happen?
Earlier in 1570 Nobunaga had invaded Echizen to attack the Asakura. Azai Nagamasa, married to Nobunaga's sister Oichi, was allied to the Asakura by older obligation and turned on Nobunaga mid-campaign, trapping him between two armies.
Nobunaga escaped in the retreat known as the Kanegasaki withdrawal, with Toyotomi Hideyoshi commanding the rearguard. Anegawa, two months later, was the counterattack.
Forces and sides
Figures in the chronicles run to roughly 28,000 on the allied side against roughly 18,000 for the Azai and Asakura. As usual, these come from later compilations and should be read as impressions of relative scale.
What happened?
The two armies met across the Ane river, which was shallow enough to fight in. The Oda faced the Azai on the right, the Tokugawa faced the Asakura on the left, and the fighting was largely a straight contest in and across the water.
The Azai attack on the Oda line reportedly pushed it back through several ranks. On the other flank, the Tokugawa broke the Asakura, then wheeled into the flank of the Azai force, which collapsed.
Turning point
The Tokugawa success against the Asakura, and the decision to turn against the Azai flank rather than pursue, is what won the day. The Tokugawa performance at Anegawa is one reason Nobunaga treated the alliance as valuable rather than as a client relationship.
Outcome
The Azai and Asakura withdrew into their own territories. Nobunaga could not follow up immediately: within weeks he was fighting the Ikko league at Ishiyama Honganji, and later that year was besieged in Omi in the Shiga campaign.
Both houses were destroyed in 1573, when Nobunaga finally had the freedom to finish them. Nagamasa died at Odani Castle; Oichi and her three daughters were sent out to Nobunaga.
Why it mattered
Anegawa shows what Nobunaga's position actually looked like in the early 1570s: winning battles while surrounded by enemies on every side, and unable to convert wins into security.
It also matters for what came later. Oichi's three daughters became, in turn, the mother of Toyotomi Hideyori, the wife of a senior lord, and the wife of the second Tokugawa shogun — which is how the Azai bloodline ended up on both sides of the final war.
