北洋水師
The Beiyang Fleet had completed escorting a convoy to the mouth of the Yalu River, and was returning to its base at Lüshunkou when it was engaged by the Japanese navy. On paper, the Beiyang Fleet had the superior ships, included two ironclad battleships, and , for which the Japanese had no counterparts. The Beiyang Fleet could also call on the assistance of numerous military advisers, including Prussian Army Major Constantin von Hanneken, recently from Korea, who was appointed as the naval adviser to Admiral Ding Ruchang. W. F. Tyler, a sub-lieutenant in the Royal Navy Reserve and an Imperial Maritime Customs officer, was appointed as von Hanneken's assistant. Philo McGiffin, formerly an ensign in the U.S. Navy and an instructor at the Weihaiwei naval academy, was appointed to as an adviser or co-commander.