The Second Mongol Invasion of Japan - The Divine Wind

In 1281, the Mongol-led Yuan dynasty launched the largest military expedition ever directed against Japan. Coming only seven years after the failed invasion of 1274 (read more here), the second campaign was an enormous undertaking involving forces from Mongolia, China, Korea, and territories formerly controlled by the Southern Song. The invasion, known in Japanese history as the Kōan no eki, or Kōan War, ultimately failed. Japanese military preparations, determined resistance, logistical difficulties, and a devastating typhoon combined to destroy the Yuan expedition.
The campaign became one of the most famous episodes of medieval Japanese history and contributed to the later development of the idea of the kamikaze, or divine wind. Yet the traditional story that a storm alone saved Japan oversimplifies what was actually a prolonged military struggle. Japanese defenses had already prevented the invaders from achieving their primary objective before the typhoon struck.

Kublai Khan and the Road to War
The invasion originated in the ambitions of Kublai Khan, grandson of Genghis Khan and founder of the Yuan dynasty in China. During the thirteenth century, Mongol power expanded across much of Eurasia. Kublai completed the conquest of the Southern Song in 1279, giving him control over the richest and most populous parts of China as well as access to considerable maritime resources.
Japan, however, refused to submit to Mongol demands. Kublai had sent diplomatic missions requesting Japanese recognition of Yuan authority, but the Kamakura shogunate did not accept the demands. After the first invasion of 1274 failed, Kublai continued to pressure Japan diplomatically while simultaneously preparing for another military expedition.
The conquest of the Southern Song was particularly important for the second invasion. The Yuan government could now mobilize large numbers of Chinese troops, sailors, shipbuilders, and ships. The result was an expedition on a scale vastly greater than the first invasion.

Preparing for the Second Invasion
The Japanese government understood that another invasion was likely. Following the 1274 campaign, the Kamakura shogunate strengthened the defenses of northern Kyushu, particularly around Hakata Bay.
One of the most important measures was the construction of a long coastal defensive wall known as the Genkō Bōrui. Built from stone and other materials, the fortification extended for roughly 20 kilometers along strategic sections of the coast. Japanese warriors were also stationed in Kyushu, while coastal patrols monitored the approaches to the island.
These preparations fundamentally changed the military situation. During the first invasion, Yuan forces had been able to land and maneuver relatively freely. In 1281, the Japanese intended to prevent the invaders from establishing a secure beachhead.
The Yuan forces were also reorganized into two major fleets. The Eastern Route Army sailed from Korea, while the much larger Southern Route Army, sometimes called the Jiangnan Army, was assembled in southern China. Historical sources give varying figures, but the combined expedition is often estimated at around 140,000 soldiers and sailors and approximately 4,400 ships. Because medieval sources frequently exaggerated military numbers, these figures should be treated cautiously.

The Eastern Route Army Attacks
The Eastern Route Army departed from Korea in May 1281. Its first targets were once again the islands of Tsushima and Iki, which stood between Korea and Kyushu.
Tsushima was attacked in June, followed shortly afterward by Iki. The island defenses were overwhelmed, and the Yuan forces continued toward Kyushu. Their objective was to attack Hakata Bay and establish a position from which the larger Southern Route Army could join them.

But the Japanese were ready.
When Yuan forces approached Hakata Bay, Japanese warriors moved rapidly to confront them. The defensive wall prevented the invaders from easily advancing inland, while Japanese fighters used small boats to attack Yuan vessels. Rather than allowing the Yuan army to establish a permanent base on shore, the Japanese repeatedly harassed the fleet and forced the invaders to remain vulnerable offshore.
This was a crucial difference from 1274. Japanese commanders had learned from the first invasion and adapted their tactics.

Samurai Versus the Yuan Army
The second invasion also demonstrated the different military traditions present in East Asia.
The Yuan army was not simply a Mongol cavalry force. It was a multinational military organization incorporating Mongol and Central Asian warriors, Chinese troops, Korean soldiers, sailors, and personnel from the recently conquered Southern Song territories.
The Mongols had built an empire based partly upon highly mobile cavalry warfare. Japan, however, forced them into a naval campaign and amphibious assault. This eliminated many of the advantages associated with steppe warfare, forcing an expert cavalry force to fight as inexperienced sailors.
The Japanese also used aggressive nighttime attacks. Small groups of warriors approached Yuan ships, boarded them, and attempted to kill soldiers and commanders before withdrawing. Such raids placed additional pressure on an already crowded fleet.
The Yuan army therefore faced an unusual problem: it had to maintain a huge invasion force at sea while being denied a secure logistical base on Japanese territory.

The Southern Route Army Arrives
The Southern Route Army was supposed to provide the decisive numerical advantage. It was substantially larger than the Eastern Route Army, but it was delayed by logistical and organizational problems.
The two forces therefore failed to achieve the perfectly coordinated attack envisioned by Yuan planners.

When the larger fleet eventually reached Japanese waters, the invaders still encountered determined resistance. The Japanese continued to defend the coastline and attack the ships. Instead of quickly conquering northern Kyushu, the Yuan forces became increasingly concentrated aboard their vessels.
This created a dangerous situation. Thousands of men were crowded onto ships for extended periods, supplies were difficult to maintain, and the fleet was exposed to weather and Japanese attacks.
The invasion had become a war of attrition.

The Typhoon of 1281
The decisive disaster came in August, as a powerful typhoon struck the Yuan fleet while it was concentrated around the waters of northern Kyushu. The storm damaged or destroyed large numbers of vessels and caused enormous casualties. Ships were smashed against one another, driven onto the shore, or overwhelmed by waves.
The Japanese subsequently remembered the storm as a kamikaze, meaning divine wind. The term became deeply associated with the belief that the gods had protected Japan from foreign conquest.
The storm, however, should not be regarded as the only reason for the Yuan defeat. Japanese resistance had already prevented the invaders from achieving their principal objective: establishing and maintaining a secure base in Kyushu.
The typhoon delivered the final catastrophe to an expedition that was already facing serious military and logistical problems.
Recent archaeological discoveries have provided additional evidence for the scale and nature of the disaster. In 2023–2024, archaeologists investigated another wreck in Imari Bay near Takashima Island. Artifacts recovered from the vessel included weapons, arrows, ceramics, and other objects, providing rare physical evidence of the 1281 expedition.

Why Did the Second Invasion Fail?
The failure of the invasion resulted from several interconnected factors.
First, Japanese preparations were far superior to those of 1274. The coastal fortifications prevented easy landings and restricted Yuan movement.
Second, the Japanese maintained persistent military pressure. Samurai forces did not simply wait behind the walls. They attacked Yuan troops and ships, particularly through small-scale raids.
Third, the Yuan invasion suffered from logistical difficulties. Maintaining a huge army by sea was extraordinarily complicated. The Southern Route Army's delayed arrival undermined the original strategy.
Fourth, the Yuan forces were operating in unfamiliar maritime conditions. The invasion required coordination between enormous fleets originating from different regions.
Finally, the typhoon destroyed much of the remaining expeditionary force. The combination of Japanese resistance and environmental disaster made continued invasion impossible.

The second Mongol invasion had profound consequences for Japan.
The victory strengthened the prestige of the Kamakura shogunate and encouraged the belief that Japan had been protected by divine forces. The term kamikaze subsequently became one of the most enduring symbols associated with the invasions.
Yet victory also created problems for the Japanese government. Unlike wars in which an enemy's territory was conquered and plundered, the Japanese defenders gained little material wealth from defeating the Yuan. Samurai warriors expected rewards for their service, but there was no large body of conquered territory that could easily be distributed.
This contributed to financial and political difficulties for the Kamakura shogunate in the decades that followed.
The invasions nevertheless had an enduring place in Japanese historical memory. They represented one of the rare occasions when Japan faced a major external invasion by a powerful continental empire. The failure of Kublai Khan's armies also marked an important limit to Yuan expansion.
The second invasion therefore occupies a unique place in medieval history: it was simultaneously a clash of empires, a naval disaster, a triumph of defensive warfare, and the origin of one of Japan's most famous historical legends.

Bibliographical References

Turnbull, Stephen. The Mongol Invasions of Japan 1274 and 1281. Osprey Publishing, 2010. ISBN 978-1846034564.

Conlan, Thomas D. In Little Need of Divine Intervention: Takezaki Suenaga's Scrolls of the Mongol Invasions of Japan. Cornell University Press, 2001. ISBN 978-1880656803.

Rossabi, Morris. Khubilai Khan: His Life and Times. University of California Press, 1988. ISBN 978-0520067400.