# 【67-9】備えあれば勝機あり！弘安の役で真価を見せるガッチガチな石壁【COTEN RADIO モンゴル帝国襲来編9】

- Show: 歴史を面白く学ぶコテンラジオ （COTEN RADIO）
- Published: 2026-10-15
- Canonical: https://podc.club/en/episode/1450522865_55cbc5af600f.html
- Audio: https://anchor.fm/s/8c2088c/podcast/play/125576079/https%3A%2F%2Fd3ctxlq1ktw2nl.cloudfront.net%2Fstaging%2F2026-8-11%2F1a541365-038e-abd3-2380-357c952d5c1e.mp3
- Source: Edited from a machine transcript of the first 30 minutes of the episode. Not an official summary.

In the 1281 Kōan Invasion, stone walls and barricades built along Hakata Bay's shoreline stopped the Mongol forces from landing, forcing a two-month standoff at sea. While conventional history credits a typhoon—the so-called 'divine wind'—as the decisive blow, historian Hattori's newer theory argues that fierce fighting continued after the storm, pointing to a more complex picture of Japan's victory.

## What this episode answers

### How did the Genkō bōrui (stone wall) function during the Kōan Invasion and prevent a landing?

A stone wall 1 jō 3 shaku tall ran along the coastline, backed by wooden barricades at the water's edge; combined with Hakata Bay's naturally shallow draft that kept large warships away from shore, the Mongol forces could not land en masse and withdrew to Shikanoshima.

### How did the two-month battle in Hakata Bay unfold?

Warrior bands led by the Iyo navy attacked the Mongol fleet—whose ships were chained together—while local fighters pinned the landing force on Shikanoshima; the Mongol army fell back to Iki Island to await the Kōnan Army, whose departure had been delayed by a full six weeks.

### What internal conflicts were tearing apart the Mongol forces?

Eastern Route Army commanders Khindun, Hung Ch'a-ch'iu, and Kim Panggyŏng were at odds; Hung Ch'a-ch'iu's habit of acting as a Mongol despite his Goryeo origins had earned deep resentment, while Kōnan Army commander Fan Wenhu carried little authority as the losing general from the Bun'ei Invasion, leaving the entire force without a credible leader.

### Where does the conventional typhoon narrative differ from Hattori-sensei's new theory?

The conventional view holds that the typhoon sank nearly the entire fleet and killed more than 100,000 men, ending the invasion at a stroke; Hattori's theory counters that the Kōnan Army was largely destroyed near Takashima (Nagasaki) while the Eastern Route Army on Shikanoshima survived relatively intact, with two more major engagements deciding the outcome after the storm.

### Did fighting continue after the typhoon, and what did Takezaki Suenaga do?

Four days after the typhoon, Japanese forces swept Hakata Bay and then defeated the surviving Mongol troops on Takashima, securing victory; Takezaki Suenaga immediately volunteered to pursue the fleeing Fan Wenhu, but discovered he had left his own ship moored in Hakata Bay and had no way to give chase.

## Article

## The Stone Wall That Sealed Hakata Bay

Seven years after the Bun'ei Invasion, in 1281, the Mongol Empire dispatched the Eastern Route Army—40,000 strong—from Happo in Korea. When that force entered Hakata Bay after departing on the 3rd day of the 5th month, the soldiers were met by a stone wall stretching as far as the eye could see along the entire coastline. This was the Genkō bōrui (元寇防塁), standing 1 jō 3 shaku tall. Banners flew from the top in an unbroken line, sharpened wooden stakes were jammed together without gaps, and at the water's edge a tangle of abatis barricades barred any approach to the beach.

Hakata Bay is naturally shallow; large warships cannot get close to shore, so landing troops required repeated runs in small boats. The wall and barricades made a swift, concentrated landing impossible. The Mongol force gave up on the beach and fell back to Shikanoshima.

## Two Months of Fighting on Hakata Bay

Japanese warrior bands launched attacks against the Mongol fleet anchored in the bay. The Iyo navy (from present-day Ehime Prefecture) was particularly noted for its role. The Mongols had chained their ships together and met approaching Japanese vessels with crossbow fire, yet the warriors pressed through the barrage. On Shikanoshima, local fighters kept attacking the landed Mongol troops, successfully bottling the enemy inside the bay.

Meanwhile, the Kōnan Army—assembled from southern China—had still not arrived. The Mongol forces withdrew all the way to Iki Island to wait. The Kōnan Army had not even departed until the 18th day of the 6th month, a full six weeks late, and the long open-ocean crossing from southern China was subject to currents and winds that scattered ships to different landfall points. Coordinating a multi-ethnic composite force added another layer of difficulty; even relaying a change of rendezvous point was no simple matter.

## Collapse from Within

Deep fault lines were opening inside the Mongol command. The three Eastern Route Army commanders—Khindun, Hung Ch'a-ch'iu, and Kim Panggyŏng—had fallen into bitter rivalry. Hung Ch'a-ch'iu was Goryeo-born yet conducted himself as a Mongol, earning intense resentment from the Goryeo rank and file; he had previously slandered Kim Panggyŏng before the king, publicly humiliating him, so the Goryeo troops had no intention of following Hung's orders. Kōnan Army commander Fan Wenhu (范文虎) carried the stigma of defeat in the Bun'ei Invasion and inspired little confidence among the southern Song troops under him. Disease broke out, and some commanders began calling for a retreat.

## The Typhoon—Conventional Wisdom versus Hattori's New Theory

On the 30th day of the 7th month (around August 23 on the solar calendar), a powerful storm built overnight into a full typhoon. The conventional view holds that the typhoon sank almost the entire fleet, killing more than 100,000 men between combat deaths and drowning, and that the surviving Japanese forces then mopped up the remnants. Court diaries recorded that "high and low alike celebrated greatly" and that "the power of the gods was plainly demonstrated." Buddhist circles credited the monk Eison (叡尊), and the victory was understood as divine protection.

Hattori-sensei's revisionist theory reads the evidence differently. The Kōnan Army, still near Takashima (Nagasaki Prefecture), took the full brunt of the typhoon and was largely destroyed—an operation that was arguably reckless from the start, with most of the fleet likely caught by the storm before ever reaching its objective. But the Eastern Route Army, dug in on Shikanoshima, came through the storm in relatively better shape. That the typhoon struck is confirmed by Mongol and Goryeo records, Japanese records, and recently discovered wrecks on the seabed alike.

## The Fighting After the Storm—and Takezaki Suenaga's Moment

Four days after the typhoon (around August 5 on the solar calendar), Japanese forces conducted a sweeping engagement in Hakata Bay, then struck and destroyed the remaining Mongol troops on Takashima. Under Hattori's framework, it was only after these two hard-fought battles that the Kōan Invasion ended in Japanese victory. Both the old and new theories agree the typhoon was decisive, but the current scholarly consensus is that Japan did not win by the typhoon alone.

One memorable episode from this moment involves Takezaki Suenaga (竹崎季長)—the warrior whose commissioned scroll paintings, the *Mōko Shūrai Ekotoba*, are the primary visual record of the invasions. Word reached him from eastern warriors just after the storm that Fan Wenhu was fleeing. Suenaga immediately volunteered to pursue him, but as he rushed to notify the commander, Shōni, he realized that Shōni was not at the main camp at Ikimatsuhara—he was at the Dazaifu family residence eight kilometers to the east. And that is when it hit him: his own ship was still moored back in Hakata Bay. He had nothing to sail in. On that wonderfully deflating note, the episode closes.

## Takeaways

- The Genkō bōrui combined with Hakata Bay's shallow waters denied the Mongols a rapid landing and made a two-month defensive battle possible—a rare case of pre-battle preparation working exactly as intended.
- The typhoon was the decisive blow, but Japan's victory resulted from multiple interlocking factors: the tenacity of its warrior bands, serious internal divisions in the Mongol command, and the structural difficulties of a long-range, multi-ethnic amphibious operation.
- The Mongol Empire's fundamental weakness was its naval power: a composite-nationality force attempting a major overseas assault was stretched to its limits in both command cohesion and logistics.