The allied force of about 150 Joseon and Ming Chinese ships, led by admirals Yi Sun-sin and Chen Lin, attacked and either destroyed or captured more than half of the 500 Japanese ships commanded by Shimazu Yoshihiro, who was attempting to link-up with Konishi Yukinaga.

Due to setbacks in land and sea battles, the Japanese armies had been driven back to their network of fortresses, or wajō (和城), on the southeastern Korean coast.

[9] The Sunch'on wajō was the westernmost Japanese fortress and contained 14,000 troops commanded by Konishi Yukinaga, who was the leader of Japan's vanguard contingent during the first invasion, in 1592.

Yi argued that Konishi, who commanded one of the largest wajō, would be allowed to escape if the allies were to leave and fight elsewhere.

[12] On 15 December, about 20,000 Japanese troops from the wajō of Sach'on, Goseong, and Namhae boarded 500 ships and began to mass east of the Noryang Strait in an attempt to break the allied blockade of Sunch'on.

Shimazu knew that Konishi was trying to cause disunity within the Joseon-Ming alliance and hoped that they would be busy elsewhere or still blockading the Sunch'on wajō and thus vulnerable to an attack from their rear.

[12] On 15 December, a huge Japanese fleet was amassed in Sach'on Bay, on the east end of the Noryang Strait.

[15] The Ming fleet consisted of six large war junks (true battle vessels most likely used as flagships) that were driven by both oars and sails, 57 lighter war ships driven by oars alone (most likely transports converted for battle use),[16] and two panokseon provided by Yi.

The allied fleet was outnumbered, but made up for it with ships which, on average, had superior firepower and heavier, more sturdy construction.

[18] As in Yi's previous battles, the Japanese were unable to respond effectively as the Korean and Chinese cannon fire movie .

[citation needed] Song Hui-rip, the captain of Yi's flagship, was struck in the helmet by an arquebus ball and fell unconscious for a time.

The Japanese sustained heavy damage and began to retreat along the south coast of Namhae Island, towards Pusan.

For the remainder of the battle, Wan wore his uncle's armor and continued to beat the war drum to let the rest of the fleet know that the Admiral's flagship was still in the fight.

[24] Konishi Yukinaga left his fortress on 16 December and his men were able to retreat by sailing through the southern end of Namhae Island, bypassing both the Noryang Strait and the battle.

Konishi Yukinaga, Shimazu Yoshihiro, Katō Kiyomasa, and other Japanese generals of the Left Army congregated in Busan and withdrew to Japan on 21 December.