Japan's Rio Grande

[The Koromo River in Southern Iwate - Japan is on the left while the Emishi lands are on the right.]

One of the defining characteristics of Japan is that it is an island nation; there are no land borders! But, this has not always been the case.

For some 300 years or more the Koromo River in Southern Iwate served to mark the boundary between the expanding Yamato state (what we now call Japan) and the retreating Emishi.

At one time the Emishi occupied nearly all of Honshu. By the mid eighth century, however, they had been pushed back to present day Miyagi and the rest of Northern Tohoku. About this time too, a group of ten districts were created South of the Koromo River called the Koromo Districts or the Nearby Emishi Districts. Here Japanese adventurers and Emishi dwelt in an uneasy proximity much like the American Wild West under the rule of Emishi collaborators!

So, when a Yamato army of 5 or 6,000 camped on the North bank of the Koromo River in 789 it was a deliberate act of provocation. When Minamoto no Yoriyoshi was appointed governor of the region in 1053 he did not dare to cross the Koromo River to take up his post until the Emishi House of Abe was defeated in the Earlier Nine-Year War; 1062.

The Latter Three-Year War ended in 1087. In an act of defiance the Emishi victor, Fujiwara no Kiyohira, erected his home/fort, Hiraizumi Mansion, South of the Koromo River in Japanese Territory!

Today the Koromo is a little known and under-appreciated stream in a remote spot in the sticks but it was once the Rio Grande of Japan!