The incident occurred when a Japanese battleship, the Unyo, sent a small boat to Ganghwa Island as a demonstration of strength by the Japanese government and was attacked by cannon from Ganghwa Island whereupon the battleship 'returned' fire.
日本政府が示威で江華島沖に送った軍艦雲揚(軍艦)から出た小船に江華島の砲台から発砲、雲揚が「応戦」した事件である。