[2] There is no agreement among contemporary sources on the exact numbers and composition of each fleet,[3] but both were of a similar size, and the battle is considered to be one of the Imperial Japanese Navy's greatest victories.

Lastly, if the Combined Fleet was defeated and consequently lost command of the sea, the bulk of the army would remain in Japan and prepare to repel a Chinese invasion, while the Fifth Division in Korea would be ordered to hang on and fight a rearguard action.

[5] With tensions with Japan increasing over the situation on the peninsula, the Chinese government chartered three steamers to carry reinforcements to Korea in late July to bolster their position there.

[6] A Japanese force consisting of the cruisers Akitsushima, Yoshino and Naniwa intercepted the three Chinese warships off Pungo Island, precipitating the action.

[8] On the same day, without even notifying Li Hongzhang, he left Weihaiwei with eleven warships and seven torpedo boats and headed for the Korean coast, while the damaged Jiyuan sailed to Lüshunkou for repairs.

However, the abrupt change in the weather made the patrolling of the Korean waters more arduous, especially for the small torpedo boats and consequently the Chinese fleet returned to Weihaiwei on 28 July.

The Chinese warships immediately resupplied themselves with coal while the weather improved, and the main force of the Beiyang Fleet was put to sea again on the following day but without the torpedo boats, heading for the Korean coast.

[8] At the beginning of September, Li Hongzhang decided to reinforce the Chinese forces at Pyongyang, by employing the Beiyang Fleet to escort transports to the mouth of the Taedong River.

[9] Admiral Ding, who then correctly assumed that the next Chinese line of defence would be established on the Yalu River, decided to redeploy the embarked soldiers there.

[9] On 16 September, at about 1:00 am, the convoy of five transport ships departed from the Dalian Bay under escort from the main force of the Beiyang Fleet which included the ironclad battleships Dingyuan and Zhenyuan, the small coastal defence battleship Pingyuan, the cruisers Jingyuen, Laiyuan, Jiyuan, Jingyuan and Zhiyuen, the small cruisers Yangwei, Chaoyong and Kwan Chia, torpedo gunboat Guangbing, the gunboats Zhennan and Zhenzhong as well as the torpedo boats Fulong and Zuo 1.

The transports, escorted by Pingyuan, Guangbing, Zhennan, Zhenzhong, together with both torpedo boats, immediately steamed up the river and dropped their anchors approximately 12–13 nautical miles (22–24 km) from the mouth of the Yalu.

The main fleet consisted of the cruisers Matsushima (flagship), Chiyoda, Itsukushima, Hashidate, the ironclads Fusō, and Hiei, under the command of Admiral Itō Sukeyuki.

[2] There were also two dispatch vessels, the converted liner Saikyō Maru under the command of Swedish-born merchant navy captain John Wilson, and the gunboat Akagi.

The four-ship group led by Pingyuan, having escorted a convoy upriver, had to catch up, and only joined the action around 2:30 pm, in time to chase off Saikyō Maru.

[2] 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.

However, examination reveals the truth about China's seemingly advantageous position, as most of their warships were over-age and obsolescent;[12] the ships were also not maintained properly and indiscipline was common among their crews.

[12] The worst feature of both Chinese battleships was actually their main armament; each was armed with short-barreled guns in twin barbettes mounted in echelon which could fire only in restricted arcs.

Corruption seems to have played a major role; many Chinese shells appear to have been filled with cement or porcelain, or were the wrong caliber and could not be fired.

The Chinese had intended to form a line abreast, but due to confusion in signals and the differing speeds of the ships, they were in a wedge formation, with the two battleships at the fore and the other vessels trailing behind on both flanks.

The flying squadron under Tsuboi increased speed from 8 to 14 knots (15 to 26 km/h; 9.2 to 16.1 mph) and headed for the very centre of the Chinese formation; the tactic held the puzzled enemy in position.

Dingyuan and Zhenyuan resisted the heaviest bombardment as a result of their armour; however, the quick firing Japanese guns decimated crews on their decks.

[19][2] The damage to Matsushima, however, was the most severe; where the lack of armour was made apparent when she was struck by two 12-inch shells that tore open the deck and ignited ready ammunition causing nearly one hundred casualties and forcing Admiral Itō to transfer his flag to Hashidate.

There is a long-repeated legend that firing the main battery directly forward resulted in the destruction of the flying bridge, but it was a mistranslation of Philo T. McGiffin's memoir, which says that he and Ding were "catapulted" by the shockwave.

[20] Now historians agree it was Japanese gunfire that destroyed the flying bridge, leaving Admiral Ding with his legs crushed under the wreckage and thus out of combat for the remainder of the battle.

According to an account from James Allan, an officer aboard the U.S.-flagged supply ship Columbia, who witnessed the battle, rumors abounded that Admiral Ding deferred command to Major Constantin von Hannecken.

[23] The Japanese had intended to swing the flying division around the right flank of the Chinese line in an encirclement, but the timely arrival of the Kuang Ping and Pingyuan, along with the torpedo boats Fu Lung (built at Schichau) and Choi Ti (a Yarrow-built vessel), diverted this maneuver.

Saikyō Maru, the converted liner, urged on by Admiral Kabayama Sukenori despite its lack of offensive armament, had been hit by four 12-inch (305 mm) shells and was left sailing virtually out of control as a result.

[27] Due to the Chinese Navy's weak preparations for the battle, faulty ammunition, and a lack of communication and discipline, which was the cause of at least one account of fragging, the Japanese forces were able to operate under very desirable conditions.

[27] A contemporary European diplomat also concurs, observing that Japan's naval "victories were due to the skill and daring of her sailors, and not to the ships which they manned".

However, this attempt to save face were insufficient, as the foreign press would come to find that many of China's claims were false, discrediting them in the eyes of the international community.