The last time Yamato was heavily involved on the continent, they were defeated militarily, and they returned to fortify their islands. So how are things looking, now?

This episode we will talk about some of what has been going on with Tang and Silla, but also touch on the Mishihase, the Hayato, the people of Tamna and Tanegashima, and more!

For more information and references, check out: https://sengokudaimyo.com/podcast/episode-140

Rough Transcript

Welcome to Sengoku Daimyo's Chronicles of Japan. My name is Joshua and this is episode 140: Improving Diplomatic Ties

Garyang Jyeongsan and Gim Hongsye looked out from the deck of their ship, tossing and turning in the sea. The waves were high, and the winds lashed at the ship, which rocked uncomfortably beneath their feet. Ocean spray struck them from below while rain pelted from above.

Through the torrential and unstable conditions, they looked out for their sister ship. It was their job to escort them, but in these rough seas, bobbing up and down, they were at the mercy of the elements. One minute they could see them, and then next it was nothing but a wall of water. Each time they caught a glimpse the other ship seemed further and further away. They tried calling out, but it was no use—even if they could normally have raised them, the fierce winds simply carried their voices out into the watery void. Eventually, they lost sight of them altogether.

When the winds died down and the seas settled, they looked for their companions, but they saw nothing, not even hints of wreckage on the ocean. They could only hope that their fellow pilots knew where they were going. As long as they could still sail, they should be able to make it to land—either to the islands to which they were headed, or back to the safety of the peninsula.

And so the escort ship continued on, even without a formal envoy to escort. They would hope for the best, or else they would explain what would happen, and hope that the Yamato court would understand.

The seas were anything but predictable, and diplomacy was certainly not for the faint of heart.

We are going through the period of the reign of Ohoama, aka Temmu Tennou. It started in 672, with the death of his brother, Naka no Oe, remembered as the sovereign Tenji Tenno, when Temmu took the throne from his nephew, Ohotomo, aka Kobun Tenno, in what would become known as the Jinshin no Ran. From that point, Ohoama continued the work of his brother in creating a government based on a continental model of laws and punishments—the Ritsuryo system. He accomplished this with assistance from his wife, Uno, and other members of the royal family—his own sons, but also nephews and other princes of the time. And so far most of our focus has been on the local goings on within the archipelago.

However, there was still plenty going on in the rest of the world, and though Yamato's focus may have been on more local affairs, it was still engaged with the rest of the world—or at least with the polities of the Korean Peninsula and the Tang Dynasty. This episode we are going to look at Yamato's foreign relations, and how they were changing, especially as things changed on the continent.

Up to this point, much of what had been happening in Yamato had been heavily influenced by the mainland in one way or another. And to begin our discussion, we really should backtrack a bit—all the way to the Battle of Baekgang in 663, which we discussed in Episode 124. That defeat would lead to the fall of Baekje, at the hands of the Silla-Tang alliance. The loss of their ally on the peninsula sent Yamato into a flurry of defensive activity. They erected fortresses on Tsushima, Kyushu, and along the Seto Inland Sea. They also moved the capital up to Ohotsu, a more easily defended point on the shores of Lake Biwa, and likewise reinforced various strategic points in the Home Provinces as well. These fortresses were built in the style and under the direction of many of the Baekje refugees now resettled in Yamato.

For years, the archipelago braced for an invasion by the Silla-Tang alliance. After all, with all that Yamato had done to support Baekje, it only made sense, from their perspective, for Silla and Tang to next come after them. Sure, there was still Goguryeo, but with the death of Yeon Gaesomun, Goguryeo would not last that long. With a unified peninsula, then why wouldn't they next look to the archipelago?

And yet, the attack never came. While Yamato was building up its defenses, it seems that the alliance between Silla and Tang was not quite as strong as their victories on the battlefield may have made it seem. This is hardly surprising—the Tang and Silla were hardly operating on the same scale. That said, the Tang's immense size, while bringing it great resources, also meant that it had an extremely large border to defend. They often utilized alliances with other states to achieve their ends. In fact, it seems fairly common for the Tang to seek alliances with states just beyond their borders against those states that were directly on their borders. In other words, they would effectively create a pincer maneuver by befriending the enemy of their enemy. Of course. Once they had defeated said enemy well, wouldn't you know it, their former ally was now their newest bordering state.

In the case of the Silla-Tang alliance, it appears that at the start of the alliance, back in the days of Tang Taizong, the agreement, at least from Silla's perspective, was that they would help each other against Goguryeo and Baekje, and then the Tang dynasty would leave the Korean peninsula to Silla. However, things didn't go quite that smoothly. The fighting against Goguryeo and Baekje can be traced back to the 640s, but Tang Taizong passed away in 649, leaving the throne to his heir, Tang Gaozong. The Tang forces eventually helped Silla to take Baekje after the battle of Baekgang River in 663, and then Goguryeo fell in 668, but the Tang forces didn't leave the peninsula. They remained in the former territories of Baekje and in Goguryeo, despite any former agreements. Ostensibly they were no doubt pointing to the continuing revolts and rebellions in both regions. While neither kingdom would fully reassert itself, it didn't mean that there weren't those who were trying. In fact, the first revolt in Goguryeo was in 669. There was also a revolt each year until 673. The last one had some staying power, as the Goguryeo rebels continued to hold out for about four years.

It is probably worth reminding ourselves that the Tang dynasty, during this time, had reached out on several occasions to Yamato, sending diplomatic missions, as had Silla. While the Yamato court may have been preparing for a Tang invasion, the Tang perspective seems different. They were preoccupied with the various revolts going on, and they had other problems. On their western border, they were having to contend with the kingdom of Tibet, for example. The Tibetan kingdom had a powerful influence on the southern route around the Taklamakan desert, which abuts the Tibetan plateau. The Tang court would have had to divert resources to defend their holdings in the western regions, and it is unlikely that they had any immediate designs on the archipelago, which I suspect was considered something of a backwater to them, at the time. In fact, Yamato would have been much more useful to the Tang as an ally to help maintain some pressure against Silla, with whom their relationship, no longer directed at a common enemy, was becoming somewhat tense.

In fact, just before Ohoama came to the throne, several events had occurred that would affect the Silla-Tang alliance.

The first event is more indirect—in 670, the Tibetan kingdom attacked the Tang empire. The fighting was intense, and required serious resources from both sides. Eventually the Tibetan forces were victorious, but not without a heavy toll on the Tibetan kingdom, which some attribute to the latter's eventual demise. Their pyrrhic victory, however, was a defeat for the Tang, who also lost troops and resources in the fighting. Then, in 671, the Tang empire would suffer another loss as Silla would drive the Tang forces out of the territory of the former kingdom of Baekje.

With the Baekje territory under their control, it appears that Silla was also working to encourage some of rebellions in Goguryeo. This more than irked the Tang court, currently under the formal control of Tang Gaozong and the informal—but quite considerable—control of his wife, Wu Zetian, who some claim was the one actually calling most of the shots in the court at this point in time. Silla encouragement of restoration efforts in Goguryeo reached the Tang court in 674, in and in 675 we see that the Tang forces were sent to take back their foothold in the former Baekje territory. Tang defeated Silla at Gyeonggi, and Silla's king, Munmu, sent a tribute mission to the Tang court, apologizing for their past behavior.

However, the Tang control could not be maintained, as they had to once again withdraw most of their troops from the peninsula to send them against the Tibetan kingdom once more. As soon as they did so, Silla once again renewed their attacks on Tang forces on the peninsula. And so, a year later, in 676, the Tang forces were back. They crossed the Yellow Sea to try and take back the Tang territories on the lower peninsula, but they were unsuccessful. Tang forces were defea...