The occurred on 28 January 1868 during the Boshin War in Japan, in the area of Awa Bay near Osaka. Involving ships of the Tokugawa shogunate and Satsuma vessels loyal to the imperial court in Kyoto, the battle was the second naval battle in Japanese history between modern naval forces (after the 1863 Battle of Shimonoseki Straits). Enomoto Takeaki led the shogunal navy to victory at Awa, in one of the few Tokugawa successes of the Boshin War, one day after the start of the land Battle of TobaâÂÂFushimi (which the shogunate lost to the Imperial forces).
The Satsuma Domain was preparing to return its troops to Kagoshima aboard two transports, the and the , protected by the Satsuma warship Kasuga stationed in Hyà Âgo harbour. The shogunal navy under Enomoto Takeaki was nearby with the steam frigate Kaiyà  Maru as its main unit, and had been supporting the Battle of TobaâÂÂFushimi from the sea. Enomoto's fleet moved to blockade the withdrawal of the Satsuma ships.
On 28 January, in the early morning, the Satsuma ships left Hyà Âgo harbor. Heiun left through the Strait of Akashi, and Kasuga went south with Shà Âà  towards the Kitan Strait. Kaiyà  Maru pursued and prepared for combat. At a distance of 1,200âÂÂ2,500 meters, Kaiyà  Maru fired about 25 times on the two Satsuma ships, and Kasuga responded with 18 shots, without significant damage to either side. However, as more Shogunate navy ships had arrived (the Banryà « and Shokaku), Kasuga broke off the engagement, and, being faster than Kaiyà  Maru, escaped to Kagoshima. Unable to flee, Shà Âà  was run aground at and was destroyed by her crew. Looking at the burning Shà Âà Â, Enomoto expressed admiration at the fight put on by his enemies: .
The future Imperial Japanese Navy Fleet Admiral Tà Âgà  Heihachirà  was a gunner aboard Kasuga during the engagement.