The Chinese Beiyang Fleet and the Imperial Japanese Navy reflected fundamentally different ideas about modern naval warfare. China's fleet was anchored by two German-built ironclad battleships, Dingyuan and Zhenyuan, whose 12-inch Krupp guns and thick armor represented the old doctrine of heavy firepower and protection. The Japanese fleet, by contrast, was built around speed and volume of fire. Their ships, many constructed by Armstrong Whitworth in England, carried batteries of quick-firing guns that could pour out shells far faster than the Chinese could reload their heavier weapons. Japan's strategy was straightforward: gain command of the sea, transport troops to the Korean mainland, and force a decisive naval battle. The Chinese strategy was to escort troop transports and avoid a fight they were not sure they could win.

The fleets met in the Yellow Sea off the mouth of the Yalu River, though the battle took place in open water, not in the river itself. The Chinese formed a rough line abreast, while the Japanese approached in line ahead, their fleet divided into a main body and a fast flying squadron under Admiral Tsuboi Kozo. The flying squadron, led by the cruiser Yoshino, exploited its speed to circle the slower Chinese formation, raking ships from multiple angles. The Chinese fought back fiercely. The battleships Dingyuan and Zhenyuan absorbed tremendous punishment but refused to sink, their German armor proving its worth. But the lighter ships around them were overwhelmed. The cruiser Zhiyuan, listing and burning, made a desperate attempt to ram a Japanese vessel before exploding and sinking with nearly her entire crew. Jingyuan burst into flames after sustained fire and rolled over. By the time the Japanese broke off the engagement, five Chinese warships had been sunk.

The battle's lessons reshaped naval thinking worldwide. The quick-firing gun, which could fire ten rounds in the time it took a heavy breech-loader to fire one, had proven decisive. Speed and maneuverability had allowed the Japanese flying squadron to dictate the terms of the engagement, choosing when and where to concentrate fire. The Chinese ironclads had survived, vindicating their armor to some degree, but they had been unable to protect the cruisers around them. The Beiyang Fleet, though not destroyed, retreated to Weihaiwei and never again challenged the Japanese for control of the sea. Japan was free to transport troops and supplies across the Yellow Sea, determining the outcome of the war on land as well.

The human cost was steep on both sides, though the Chinese losses were catastrophic. Of the 270 men aboard Jingyuan, only seven survived. Zhiyuan lost all but seven of her 246 crew. Captain Deng Shichang, who ordered Zhiyuan's final charge, became a national hero in China. A training ship in the modern PLA Navy bears his name, and a full-scale replica of Zhiyuan was built at the Port of Dandong in 2014 as a floating museum. The wreck of the original was discovered in 2013 after a 16-year search, and over 100 artifacts have been recovered, including weapons, ship components, and personal items of the crew. The battle established patterns that would echo through the next century of East Asian conflict: a modernizing Japan asserting power over an empire struggling to reform, with Korea and Manchuria as the contested ground between them.