The Great Khan Khubilai had always had something of a chip on his shoulder. He was constantly compared to his grandfather, the Father of the Mongol nation himself, Lord Genghis… and he never did quite fill those footprints. Whereas Genghis had forged his empire from nothing with little but a leather saddle, a wooden bow, and his iron will… Khubilai had grown up in the lap of luxury, a coddled imperial prince who had been handed supreme power when his older brother, Mongke, had been killed while besieging the Song Chinese bastion of Chongqing. Moreover, he had grown up not in Mongolia, but in Northern China, surrounded and educated by Chinese, his mother was a Nestorian Christian, many of his advisers were Chinese Buddhists and Confucians… and many of his own kin within the Borjigin Clan considered him not Mongol enough to rule the empire. He’d grown up soft.

That had exploded shortly after his accession in 1260, when his khurultai had been declared illegitimate by other branches of his family, who instead back his younger brother – Ariq’s – claim. Ariq Boke “the Wrestler” was much more the “traditional Mongol,” having grown up in the heartlands of the Khentii Mountains, while Khubilai have been lavished upon in the flesh pots of the south. The resultant Toluid Civil War – far from strengthening the Mongol Empire – had forever shattered it, leaving Khubilai the Great Khan in-name-only, and more and more the founder of the Yuan Empire of China, rather than the torchbearer of the Universal Empire of the Mongols that his grandfather had envisioned.

So yeah, Khubilai had a chip on his shoulder. He wanted to be as great as his forebears. And in the Mongol way of thinking, there was only one real way to do that: conquest. Now, to be fair, it was Khubilai who would finally complete the most difficult conquest the Mongols had ever faced – the Song Chinese and their stalwart, intransigent rearguard south of the Yangtze River. But conquest empires are ever-churning, all-devouring, and never sated; the more the grow, the more they must continue to feed. To idle out it to begin to die. Additional growth was not just desired, but positively required. The Great Khan had ever-spiraling bills to pay, after all – and at least as important, Mongol princes to pay stipends to, or else risk them openly revolting against him (and such conflicts were by their very nature the opposite of profitable, even if victorious). Korea had already long been *mostly-*peaceably folded into the Mongol Empire, which meant that the next logical step would be to move beyond that peninsula, and to the mysterious, archipelagic, hermit kingdom beyond the waves: Japan.

What that meant was that Khubilai figured that if he proved himself capable of reestablishing diplomatic ties with the land of the Rising Sun as a tributary state of his great empire, then he would prove himself both a great conqueror in the eyes of his Mongol brethren and simultaneously establish himself as a great Chinese ruler on their own terms. As a quick note here, Khubilai was a careful student of Chinese history and had chosen for himself a past ruler on whom he wished to model his own reign and dynasty; who else but that last great ruler of the Middle Kingdom, the Übermensh himself, Tang Taizong? It would be a tremendous victory that no other Mongol leader could hope to duplicate: the Great Khan that sailed across the sea and conquered the edge of the world. And so what if no Mongol had ever substantively engaged in sea-based amphibious operations? I mean, how hard could it be? We'll just get the Koreans to give us a few lessons, and we'll be good to go. It'll be fine.

For their part, the Koreans were no great friends of the Japanese. Since at least the early 1220s, the peninsula had been under a near continuous assault by Japanese pirates and coastal raiders that patrolled up and down the coasts of the Eastern Sea looking for easy plunder, no matter what banner it might be sailing under: Korean, Song Chinese, Mongol, whatever. These pirates had long been known by the derisive name Wo or Weigu in Korean, Wokou in Chinese, or Wako in Japanese. Wo both referred to the supposed origin of the Japanese people themselves, as well as referencing dwarfism in a pejorative sense, & kou meant bandits... so, the Japanese “bandit dwarves” Wokou.

As with many such freebooters across time, the Wokou pirate bands typically hid themselves in the innumerable, coves and hideaways that dotted the thousands of tiny islets and archipelagos all the way from Hokkaido to Hainan. They had no official backing by either the Japanese emperor nor the Shogunate government. Moreover, even though they were commonly thought of as being Japanese pirates, they were again in extremely common fashion, typically a far more pell-mell mixture of just about every ethnicity, race, class and type of person that might exist along the Pacific rim. Any sailor or ship was little more than one lost shipment or untimely pirate attack themselves away from being forced by circumstance or sword point into signing on to the pirate's life and being branded an outlaw. Indeed, it was relatively common practice among the various royal courts of the dynasties to occasionally, like upon the accession of a new ruler or other such momentous events, issue a general pardon as an act of grace to such outcasts and allow them a path back to return to normal society provided, of course, as a force forever returning to a criminal lifestyle.

Thus, though the Korean kingdom was regularly harassed by pirate vessels, especially as its defensive forces were increasingly distracted by the Mongol threat to the northwest, its own court understood the independent nature of piracy well enough to know that it wasn't Japan itself sending these raiders against it and did not declare war on the island kingdom. It would occasionally send emissaries to lodge strongly worded protests against the raids with the Japanese government, but otherwise simply understood that there was little either side could really do about the problem. Moreover, once Korea had been subdued by the Mongols and its coastal defenders were able to renew their vigil against such piracy with their former vigor, the raids largely ceased by the mid 1260s. As such, neither the Korean populace nor its role court had significant interest in engaging in direct hostilities with Japan.

Khubilai, however, had other ideas. In the autumn of 1266, the Mongol Great Khan had dispatched an embassy of his own to sail for Japan in order to inform the distant kingdom that China was under new management and to invite the Japanese Emperor to be a good little vassal state and send a mission of its own to the Yuan then-capital, Shangdu, in order to offer a tribute to Emperor Khubilai. Two envoys were dispatched first to the Korean capital, then called Kangdo, and about three months later proceeded onward towards Japan in the company of two local guides. Yet by the time they'd arrived at the send-off point to the true oceanic segment of their journey, a small island called Kojaido, the two Mongol envoys had apparently been convinced by their less-than-eager Korean guides that oceanic travel to Japan was definitely not for them, and that the seas were far too rough and dangerous to make such a voyage. As such, the mission turned around incomplete, and the two Mongol envoys hastened back to China.