The ruins of the Mizuki Embankment which are now extended in Dazaifu and Onojo Cities, as well as several small embankments in Onojo and Kasuga cities, are designated as the national special historic sites respectively. Citizens of these cities are proud of those historic sites to this day. The Mizuki (it means water and a castle) Embankment was literally a huge embankment to play the role of a castle to defend the country by the water, and protect its surrounding areas from flood disasters. It was built in A.D.664 according to Nihon-shoki (the oldest chronicles of Japan). While three Kingdoms of Koguryeo, Silla and Baekje were fighting with each other on the Korean Peninsula in the former half of the 7th century, in 660, the allied military forces of the Silla Kingdom and the Chinese Tang Dynasty attacked Baekje. The Kingdom of Yamato, or Wa (the then name of Japan) dispatched its military forces to rescue Baekje, with which it had a friendly diplomatic relationship, twice, in 661 and 663. Mainly due to geographical disadvantage, Wa’s military forces were completely defeated. Historically, it is called, ‘The Battle of Baekgang (‘Hakusukinoe’ in Japanese) ’.
After its military forces retreated to its mainland, Wa, the Kingdom of Yamato, in fear of the Tang-Silla allied military forces’ counterattack, hastened to rearrange its national defense systems.
The Mizuki Embankment was one of the Kingdom of Yamato’s national defense systems. The Embankment with a length of 1.2 km, a width of 80 m, and a height of 13m was built in a few years by the rush construction work with the help of Baekje’s civil engineers who came to Japan as refugees. It was mainly because the Kingdom of Yamato was determined to defend its Dazaifu government office by this Embankment against the Tang-Silla allied military forces’ unanticipated sudden invasion into the Mizuki region from the Hakata Bay.
Fortunately, the Tang-Silla allied military forces did not invade the Kingdom of Yamato. However, the building of this Mizuki Embankment remains to remind us of the importance of Japan’s security.