The Battle of Kōan, also known as the Second Battle of Hakata Bay, was the second attempt by the Mongol-led Yuan dynasty of China to invade Japan after their failed attempt seven years earlier at the Battle of Bun'ei. In the summer of 1281, the Yuan invaded with two large armies. The Japanese defenders were aided by a major storm which sank a sizeable portion of the Yuan fleets. The invaders who reached the shore were repulsed shortly after landing. The Japanese called the opportune storm kamikaze (lit. 'divine wind'), a name later used in the Second World War for pilots who carried out aerial suicide attacks.
The first of the Southern force ships arrived on July 16, and by August 12 the two fleets were ready to attack Japan. On August 15 a major tempest struck the Tsushima Straits, lasting two full days and destroying most of the Yuan fleet. Contemporary Japanese accounts indicate that over 4,000 ships were destroyed in the storm; 80% of the Yuan soldiers either drowned or were killed by samurai on the beaches. The loss of ships was so great that "a person could walk across from one point of land to another on a mass of wreckage".
Main battles of the Kōan Campaign
Battle of Tsushima Island
On June 8, the Yuan Army landed on Tsushima island. According to the History of Yuan, the Japanese commander Shōni Suketoki and Ryūzōji Suetoki led forces against the invasion force. The expeditionary forces discharged their firearms, and the Japanese were routed, with Suketoki killed in the process. More than 300 islanders were killed.
Battle of Shika Island
On June 23, unable to land in Hataka, the Yuan fleet occupied the islands of Shika and Noko from which it had planned to launch raids against Hakata. By June 24, Mongol forces had control of most of the island, but on the morning of June 25, the Japanese army divided their force into two and attacked along Umi no Nakamichi. Several clashes followed resulting in 300 casualties for the Japanese army.
On June 26, the Japanese forces launched a surprise night attack on Zhang Cheng, his unit held their position on the ships and fought through the night. By dawn, the Japanese ships retreated. The following days, the Japanese forces again assembled a large army for battle but they were routed, many were killed or wounded.
Battle of Iki Island
On July 16, a Japanese army of approximately 10,000, led by the Matsura clan, Ryūzōji clan and Takagi clan began an all-out attack on Iki Island. On July 18, Ryūzōji Iekiyo (龍造寺家清) landed on Setoura beach and defeated the Mongol army. As a result, the Mongol army abandoned Iki Island and withdrew to Hirado Island.
Battle of Mikuriya
On 15 August, a great typhoon, known in Japanese as kamikaze, struck the Yuan fleet at anchor from the west and devastated it. Sensing the oncoming typhoon, Korean and south Chinese mariners retreated and unsuccessfully docked in Imari Bay, where they were destroyed by the storm. On August 20, Takezaki Suenaga attacked the stranded ships. After this battle, most of the commanders of the Mongol army escaped to their own country.
Battle of Taka Island
On August 22, 100,000 soldiers of the Yuan fleet remained marooned on Taka island without commanders. Upon realizing the situation, the Japanese army launched an assault. Togō Korechika, Togō Koretō, Fujiwara no Sukekado, and Shimazu Nagahisa led the charge, successfully defeating the remaining Yuan forces. They captured between 20,000 and 30,000 prisoners during the battle, killing the rest.
Aftermath
Kublai Khan began to gather forces to prepare for a third invasion attempt, but was soon distracted by events in Southeast and Central Asia, and no third attempt was ever made.