The war of 663—known in Japanese as Hakusuki-no-e-no-tatakai [白村の江の戦い 'Battle of the White Village River'] or the "Battle of the Paekchon River," after the old name for the Kŭm River—has long attracted the attention of historians and laymen alike in Japan....SOURCE: Gateway to Japan: Hakata in War and Peace, 500–1300, by Bruce L. Batten (U. Hawai‘i Press, 2006), pp. 23-25
In Kyushu ... the effects of the war were immense and long lasting.... It is no exaggeration to say that the events of the 660s and early 670s created an international boundary where none existed before. Prior to the war, there was no clear line between "us" and "them," and traffic between the Korean Peninsula and Kyushu was relatively free (although never tremendously frequent, given the dangers and the distances involved). Within a decade after Japan's defeat, such a line had come into existence (in the Korea Strait between Tsushima and Silla), and Japan had a fortified border with a single designated gateway. The gateway was Hakata, and the gatekeeper was Dazaifu, the command center south of the bay.
Of course, Yamato had long had a significant interest in northern Kyushu, and in particular Hakata, because of the area's strategic location. The most sensible way to get from Yamato to the Korean Peninsula was to go down the Inland Sea, follow the northwest Kyushu coast to Hakata, and then cut across the Genkai Sea via the islands of Iki and Tsushima. To control Hakata was thus to control access to the continent—the key to hegemony in early Japan. This is why the Iwai "rebellion" posed such a threat in the 520s, and why the court moved so swiftly to put it down. After Iwai was killed, his son offered territory near Hakata to the court (in order, according to the chronicles, to save his own skin). Soon afterward, in 536, Yamato established a line of granaries (miyake, probably best understood as supply depots) up and down the Inland Sea. Much of Fukuoka Plain was also converted into a granary at this time. In 1984, remains of sixth-century storehouses and office buildings, presumably part of this "Nanotsu Miyake," were uncovered by archaeologists working on a salvage operation near Japan Railways' Hakata Station in Fukuoka.