Two Emperors at Once: How Ashikaga Takauji Split Japan for Sixty Years

On the seventh day of the eleventh month of Kenmu 3 — December 11th, 1336 in the Western calendar — Ashikaga Takauji oversaw the enthronement of Emperor Kōmyō at Kyoto. Kōmyō was the cousin of the reigning Emperor Go-Daigo, who had reigned since 1318, who had led the revolt that destroyed the Kamakura Bakufu in 1333, and who at that moment was still alive and at large in the mountains south of the capital. By the formal logic of any imperial succession system anywhere, only one of these two men could be the legitimate emperor. By the formal logic of the Japanese imperial succession system specifically, abdication had to be voluntary and the new emperor had to be installed by ritual. Takauji had performed the ritual without the abdication. There were now two emperors.

The split that began in December 1336 lasted until October 1392, fifty-six years. It is conventionally called the Nanboku-chō period — the Period of Northern and Southern Courts. It is one of the strangest constitutional situations in any premodern political system.

How It Happened

The fork that produced two emperors had been opening for almost a century before Takauji's act of 1336. Since the late 1200s, the imperial succession had alternated between two rival imperial branches — the Jimyōin line (associated with the older imperial family of Emperor Go-Fukakusa) and the Daikaku-ji line (associated with the younger family of Emperor Kameyama). Each branch produced an emperor in turn. The compromise was unstable and bitter, and the choice of which branch to favor was one of the live questions of late-Kamakura politics.

Emperor Go-Daigo, of the Daikaku-ji line, was atypical in his determination not to abdicate after the customary period. His revolt against the Kamakura Bakufu in 1331–1333 was driven partly by his refusal to step down. When the bakufu collapsed and Go-Daigo's Kemmu Restoration began in 1333, the rival Jimyōin branch — which had been waiting for its turn — found itself indefinitely sidelined.

When Takauji broke with Go-Daigo in 1336 and needed an alternative emperor to legitimize his own government, the obvious choice was a Jimyōin candidate. Kōmyō was the son of Emperor Go-Fushimi of that line, a young man with no previous expectation of the throne who suddenly found himself sitting on it. The Daikaku-ji line continued to claim the throne through Go-Daigo and his successors at Yoshino. Both could plausibly claim legitimacy. Both did, for the next fifty-six years.

What It Meant in Practice

The two courts produced separate calendars, separate edicts, separate grants of court rank, and separate alliances with regional samurai houses. Choosing which court to acknowledge was the principal political question for every daimyō. Some, like Kusunoki Masashige and his sons, fought for the Southern Court to the death. Others, like the Ashikaga themselves, were Northern. Many switched sides repeatedly depending on local advantage.

Periodically the warriors of one court would burn the capital of the other. Kyoto changed hands multiple times. Yoshino, the mountain refuge of the Southern Court, was attacked and partially destroyed several times. The wars of the two courts were not as bloody as the Sengoku would later be, but they were chronically destabilizing — and they fundamentally undermined the legitimacy of the imperial institution by demonstrating that the throne could be in two places at once.

The Reconciliation

By 1392 the Southern Court had been militarily exhausted and the Ashikaga Shogun Yoshimitsu negotiated a settlement. The Southern Court emperor Go-Kameyama would abdicate to the Northern emperor Go-Komatsu. In exchange, the imperial succession would alternate between the two lines as it had in late Kamakura. The Southern emperor abdicated in October 1392. The promised alternation never happened. Go-Komatsu's son Shōkō succeeded him; Shōkō's brother continued; the imperial line stayed Northern through the rest of the Muromachi period and remained so.

For the modern Imperial House of Japan, the Southern Court is the legitimate imperial line. This is a Meiji-era ruling, made for political reasons: Emperor Meiji's grandfather Kōkaku had argued for the legitimacy of the loyalist Southern Court. The current emperor's official genealogy thus runs through Go-Daigo and Yoshino, not through Kōmyō and Kyoto. From the 1336 vantage point, this would have been the unexpected outcome.

Why It Mattered

The Nanboku-chō split is the largest single discontinuity in the otherwise continuous Japanese imperial line, which has been a central cultural fact of Japanese identity for fifteen centuries. It demonstrated, against all earlier theory, that the imperial institution could be politically captured and replicated. It established that warrior governments could choose their emperor, not the other way around. It legitimized, in operational terms, the principle that military power preceded ritual legitimacy.

These were the same principles that the Sengoku-era warlords would operate on a hundred years later. The Ashikaga shogunate that Takauji founded was unstable from the start, and the period from 1467 to 1573 — the Sengoku — was, in a real sense, the long aftermath of Takauji's 1336 decision. The institutional weakness he had built into the Muromachi Bakufu by tying his own legitimacy to a captive emperor produced, eventually, the warring states period that needed Oda Nobunaga to begin to repair.

"I have made one war and another after it; I have ended none of them in time."