The Mongol invasions of Japan were costly failures. According to Wikipedia, the Korean King Chungnyeol (by this time a vassal of the Mongols) was

...known as the fixer who instigated Mongol Emperor to invade Japan with voluntary and overall naval aid to invade Japan together with Mongol Empire.

No sources are cited for this assertion, but Chungyeol presumably had some influence as he was married to one of Kublai Khan's daughters. Koreans also made up a substantial proportion of both invasion forces (1274 and 1281).

The Wikipedia entry on Kublai Khan isn't much help:

Kublai decided to invade Japan, Burma, Vietnam, and Java following the suggestions of some of his Mongol officials.

Kenneth G. Henshall in A History of Japan says only that

Kublai’s next main target was southern China, the base of the Sung (Song) forces. However, he also turned his attention to Japan.

At the time of the first invasion of Japan, the Mongols had yet to conquer southern China under the Song dynasty, which surrendered two years after the first invasion of Japan.

As Japan does not seem to have been especially wealthy at the time and would thus not have provided anything like the economic benefits to the Mongols that southern China could have, what convinced Kublai Khan to invade Japan first? Was the Korean King Chungnyeol instrumental in this decision?

  • While heir, it's quite possible that Chungyeol was at Kublai Khan's court (and exerting some influence there) during his father Wonjong's reign until 1274. Jan 8, 2018 at 21:59
  • Hmm ... interesting point. I also see the same statement in Wikipedia entry on Chungyeol. Let me look at this and get back.
    – J Asia
    Jan 9, 2018 at 16:07

2 Answers 2



As Japan does not seem to have been especially wealthy at the time and would thus not have provided anything like the economic benefits to the Mongols that southern China could have, what convinced Kublai Khan to invade Japan first? Was the Korean King Chungnyeol instrumental in this decision?

There are 2 main parts to this question. The easier one is: why did Kublai Khan invade Japan before first conquering the Song Dynasty (southern China)? The answer to this 1st question gets a bit lengthy (but not too much, I hope)

As regards the 2nd question, the role of Prince Sim (諶), (posthumous title King Chungnyeol, 1274–1308) in the invasion of Japan. He was the son of King Wonjong.

1. Why did Kublai Khan invade Japan in 1274 (Bun'ei) & 1281 (Kōan)

The context of this question is, since Kublai had not completed subjugating the Southern Song Dynasty, which he did in the final battles of 1276-9, why the rush to invade Japan? What was the impetus?


The straight-forward answer is that it was to strangle the economy of the Song Dynasty because Japan was a valuable trade partner of the Southern Song Dynasty. Also, the maritime trade route with China did not have to go through Korea/Goryeo (which had already submitted to the Yuan Dynasty).

The failure to establish a positive relationship with the Japanese resulted in the invasions of 1274 & 1281.

Song coins and trade with China

In fact, China's maritime trade with Japan was so strong that the (Japanese) Kamakura bakufu suffered somewhat with debt and inflation (especially from importation of Song coins). From The Cambridge History of Japan, Volume 3 - Medieval Japan (1990), pp. 358-360:

Throughout the late Heian and early Kamakura periods, trade with the continent - Sung and Southern Sung - continued, and two results of this trade are especially significant ... One was that trade with China offered elites many products unobtainable in Japan; the other was that the trade brought in a large quantity of Sung coins. The latter was by far more important because it led to the monetization of the Japanese economy, which in turn had profound effects on the political, economic, and social history of Japan during the Kamakura and Muromachi periods. ...

Foreseeing the various difficulties to arise as a result of the economy's continuing monetization, in 1239 the bakufu was forced to issue a decree prohibiting the appointment of monks, merchants, and moneylenders to the position of deputy jito (jito-dai). Some in the warrior class had begun to appoint these men to collect dues directly from the shoen so that those who had lent money against the warriors' land could be repaid. To prevent such a development, the bakufu in 1240 admonished its retainers living in Kyoto not to indulge in luxury beyond their means. These developments, however, were only the harbinger of the much more serious consequences of monetization.

Importance of Japan to conquering the Song Dynasty

Kublai's invasion of Japan was not knee-jerk, nor taken lightly. As mentioned, it was a strategic decision taken only after numerous attempts at establishing a subordinate (tributary) relationship with Japan had failed. In my mind, King Chungyul (or Chungnyeol) was not involved in the decision-making (more below).

In total, Kublai sent emissaries to Japan six times, beginning with the first letter in 1266 (arrived 1268). A lot turns on the intention of Kublai and, as Gavin has shown in his answer, it depends on how the initial (1266) demand letter is interpreted. Was it a threat or even declaration of war? In fact, it could be a routine request or, at least, non-threatening. Kublai had friendly intentions with Japan at the beginning because the prize was always the Song Dynasty.

Again, from volume 3, pp. 414-415 (emphasis mine):

A document from the Mongols (dated 8/1266 and arriving in Japan on 1/1268) first described the Mongols' might and then recounted how they had brought peace to Koryo, explaining that the Mongol-Koryo relationship was like lord and vassal or father and son: Koryo was the Mongols' "eastern vassal state." Japan is close to Koryo, the document continued and, since Japan's founding, had normally had exchanges with China but had not yet concluded peace with it. Saying that perhaps "your honorable country" is unaware of these circumstances, the document expressed the Mongols' wish to establish friendship between the two states. The wording was courteous and did not demand Japan's submission, but it concluded that if there were no other way, the Mongols would resort to force of arms. Reminiscent of the edicts issued by the emperor in the Han Chinese state, this document coupled the Mongol sense of superiority with a Chinese moral view, following traditional Chinese foreign-policy forms. From ancient times China had, in return for the tribute goods that neighboring kingdoms brought and presented at the Chinese court, granted these states "gifts" of a higher value than the tribute, preserving a China- centered foreign-policy structure. Ever mindful of Chinese tradition, Kublai naturally patterned his actions after that policy. The type of relationship that Kublai first sought with Japan was probably this sort of tribute-gift exchange, one that combined politics, foreign relations, and economics.

Why did Kublai seek peace with Japan in 1266? The Mongols were preparing to attack the Southern Sung, and Kublai, judging the Sung to be strong, proceeded carefully with his attack plans. Part of these plans required strengthening control over Koryo. In his document Kublai referred to Koryo as the Mongols' "eastern vassal state." With Kublai's military backing, Koryo's King Wonjong had suppressed the military officials who had previously controlled national politics and had increased his own authority as sovereign. Thus, from Kublai's point of view, Koryo was indeed a newly attached country. Using the negotiations with Japan as a tool, Kublai was able to intensify his domination over Koryo. Also, in preparing to invade Southern Sung, Kublai had come to realize that Japan, even though it was a small eastern island really not worth taking, it could not be left alone. Japan traded with the Southern Sung and therefore continuously added to the Sung's financial strength. Seen in this light, Japan had to be cut off from the Sung and added to Kublai's empire. And this would be possible if Koryo were used as a go-between.

Finally, the Mongol tradition of valuing their emissaries should not be underestimated. I cannot remember how many, but some of the emissaries to Japan died. This was clearly against their strict tradition. Just as the last Shah of the Khwarezmian dynasty found out, disrespecting by shaving the heads of Genghiz Khan's two ambassadors and killing one (he was the only Muslim) led to Genghiz Khan's conquest of Khwarezmia. Japan's warrior class probably did not appreciate this aspect of Mongol diplomacy, which led to the two invasions.

2. Goryeo's Prince Sim (after 1270, Crown Prince) & Mongol invasion of Japan

Simply put, Goryeo was not significant at all to the Yuan Dynasty except as a military base to the Mongols, i.e. launching pad for the invasion of Japan. Obviously, I have no evidence that Prince Sim/Chungyul did not influence Kublai Khan to invade Japan. But, I can offer three reasons why Chungyul was "not instrumental" to the invasion of Japan:

  1. Kublai Khan was an excellent strategist. Not sure he needed help from Prince Sim (and a non-Chinggisid at that). Kublai's civil war with his youngest brother, Arigh Borke, is clear testament to his ability as he fought a near perfect campaign (a lot of troop maneuvering in China's Northern Plain and Mongolia). For reference, see operational level of war & a report by the U.S. Army's School of Advanced Military Studies (SAMS) on Mongol Warfare - PDF).

  2. Prince Sim was sent to Kublai's court whilst his father, Wonjong, was still the Crown Prince being held hostage back in Goryeo (by the Choe military regime). In 1270, King Wonjong finally ascended the throne, allowing Prince Sim to be made Crown Prince. That's why the marriage should be 1271 onwards (re Gavin's answer). In any case, Crown Prince Sim was of no significant (neither diplomatic nor military) value during his time at the Yuan court because even his father, King Wonjong, needed the help of the Mongols to (in effect) ascend the throne.

  3. Goryeo was one of Yuan Dynasty's many administrative centers, not that valuable other than a launchpad for the invasion. See Zhengdong Branch Secretariat, only useful as a vassal (tribute) and as "Japanese Expedition province".

  • +1 for effort (at least). You may well be on the right track - I hadn't thought of the trade angle in relation to the Song and will have to do a little extra reading, though I'm inclined to accept your answer. At the very least, I think you are probably right that Chungyeol was not 'instrumental'. Jul 12, 2018 at 9:31
  • @LarsBosteen - A few things (if you're interested). 1. The concept of battle-space (location) was huge for the Mongols. The Western world caught up much later, late-19th century. So, not surprising Kublai's theatre was that far. 2. That 1266 letter is much debated -- no conclusion either way. (I have it, tell me if you want to read it, can post in answer). 3. Trade is (almost) EVERYTHING to steppe nomads, hence the high esteem of emissaries. Japan's non-participation was the real impetus to the invasion. I can expand my answer if you're still keen. ;)
    – J Asia
    Jul 12, 2018 at 17:40

Before I begin to answer your question a little information is required to set the appropriate background of discussion. In 1259 the Koreans, the Goreyo at the time, capitulated to the Mongolian forces and signed a treaty making Korea a vassel of the Mongol horde than led by Möngke Khan. Subsequently in 1260 Kublai Khan comes to power inheriting his fathers conquest of China. In 1266, having nearly completed his subjugation of the Chinese peoples, Kublai Khan sent emissaries to Japan demanding Japanese subjugation. . .

Cherished by the Mandate of Heaven, the Great Mongol emperor sends this letter to the king of Japan. The sovereigns of small countries, sharing borders with each other, have for a long time been concerned to communicate with each other and become friendly. Especially since my ancestor governed at heaven's command, innumerable countries from afar disputed our power and slighted our virtue. Goryeo rendered thanks for my ceasefire and for restoring their land and people when I ascended the throne. Our relation is feudatory like a father and son. We think you already know this. Goryeo is my eastern tributary. Japan was allied with Goryeo and sometimes with China since the founding of your country; however, Japan has never dispatched ambassadors since my ascending the throne. We are afraid that the Kingdom is yet to know this. Hence we dispatched a mission with our letter particularly expressing our wishes. Enter into friendly relations with each other from now on. We think all countries belong to one family. How are we in the right, unless we comprehend this? Nobody would wish to resort to arms.

As with many Mongolian enemies the Japanese rejected the initial offer of subjugation taking great offense to it. The Mongols then made five additional ventures to Japan demanding subjugation but the ambassadors were not even permitted on the island. In 1268 Kublai Khan commisoned ships for the invasion of Japan using his marriage to the crown prince of Korea as pretext. Korean king Chungnyeol of Goryeo officially came to power in 1274, the year of the Mongolian invasion of Japan.

Now to answer your question directly, the Mongol Khan almost certainty would have eventually went to war with the Japanese people in order to expand his influence and solidify his control of eastern Asia, regardless of the economic prosperity of Japan. Sadly I could not find a date for the marriage between Chungyeol and Kublai Khans daughter, but I did find a primary source, The History of Yuan, which explicitly stated that Chungyeol had great enough influence over the Khan to convine him to go to war with the Japanese in the middle of his Chinese campaign. The history of Yuan directly states that king Chungyeol. . .

"persistently recommending an expedition to the east of Yuan's emperor in order to force Japan to become its subject."

Although a date for Chungnyeol marriage to Kublai Khans daughter is unknown, it is likely to have been prior to 1268 as this is when the Khan commissioned his ships using Korean ports. The reason for this marriage would have been completely political due to the fact that much of Korea remained in open revolt of Mongol rule until 1270. This would have given the khan great motivation to marry to the royal family in order to solidify his rule of Korea and for king Chungnyeol to potentially convince the Khan to invade Japan.

To summarize, the Korean King Chungnyeol defiantly played some role, and likely a large one, in the Mongolian invasion of Japan. As for what economic benefits the Mongolians hoped to gain, simply the expansion of the Khans ever growing power was justification enough for his going to war. Hope this helps !

  • 1
    "using his marriage to the crown prince of Korea " - might need to edit this statement. Jul 10, 2018 at 1:53
  • @axsvl77: Talk about 'revisionist history' - that would be a doozy. Jul 10, 2018 at 5:21
  • Interesting tid bit about the marriage to Jeguk, I spent so much time researching Chungnyeol I completely neglected his wife. Ill do a little more poking around and make a edit to my original post. Jul 10, 2018 at 6:21
  • Your effort so far is appreciated and I'll be interested in anything else you turn up. Jul 12, 2018 at 9:34

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.