Kemmu

Overview

Kemmu (建武) was a Japanese era name used during the Era of Northern and Southern Courts, a period of dynastic division that followed the collapse of the Kamakura shogunate. The era began in January 1334 and ran through August 1338 in the Northern Court, while the Southern Court considered it to have ended earlier, in February 1336. The era name followed Genkō and was succeeded by Ryakuō in the Northern Court, and by Engen in the Southern Court.

The era takes its name from the Kenmu Restoration period (1333–1336), the brief attempt by Emperor Go-Daigo to restore direct imperial rule after more than a century of shogunal government. During the Kemmu era, two emperors reigned: Emperor Go-Daigo in the south and Emperor Kōmyō in the north. The existence of two simultaneous emperors reflects the political fracture that defined the age.

What Defined the Era

The Kemmu era was defined by the collision between imperial ambition and samurai expectations. Emperor Go-Daigo had overthrown the Kamakura shogunate in 1333 with the help of warrior leaders such as Ashikaga Takauji and Nitta Yoshisada. Once in power, Go-Daigo sought to restore the authority of the throne, issuing edicts and appointing nobles to key posts, but he failed to reward the warriors who had made his victory possible.

The emperor’s policies alienated the samurai class, who had fought for land and recognition, not for a return to court-centred governance. Ashikaga Takauji, one of the most powerful warriors in the realm, turned against Go-Daigo in 1335. Takauji’s rebellion split the country into two armed camps: the imperial loyalists under Go-Daigo and the Ashikaga faction, which sought to establish a new shogunate.

The era also witnessed the formalisation of the Northern and Southern Courts. In 1336, Takauji installed Emperor Kōmyō on the throne in Kyoto, while Go-Daigo fled to Yoshino in the mountains to the south. From that point, the Kemmu era name was used by both courts, but with different end dates, reflecting the competing claims to legitimacy.

Key Events

In 1334, Emperor Go-Daigo promulgated a series of administrative reforms, including the restoration of the Records Office and the Court of Appeals, institutions designed to settle land disputes and reassert imperial control over appointments. These measures were central to the Kenmu Restoration’s agenda but proved difficult to enforce.

In 1335, Ashikaga Takauji left Kyoto to suppress the Nakasendai rebellion, a rising by the Hōjō clan remnants in the east. While Takauji was away, his brother Ashikaga Tadayoshi clashed with Go-Daigo’s loyalists in Kyoto, and Takauji, upon his return, openly defied the emperor. The conflict escalated into open warfare.

In 1336, Takauji defeated Nitta Yoshisada at the Battle of Minatogawa, a decisive engagement that forced Go-Daigo to abandon Kyoto. Takauji then entered the capital and enthroned Emperor Kōmyō, a prince from the Jimyōin line, as the new sovereign. Go-Daigo established a rival court at Yoshino, and the Kemmu era continued in the north until August 1338, when it was succeeded by Ryakuō.

The Name in Japanese

The era name is written 建武 in Japanese. Its kana reading is けんむ, and its romaji is Kemmu.

The name consists of two kanji:

• 建, read as ken in this word, means “to establish” or “to build.” It appears in words like 建設 (kensetsu, construction) and 建国 (kenkoku, founding of a nation). The character carries a sense of laying a foundation or setting something up deliberately.

• 武, read as mu in this word, means “military” or “martial.” It appears in 武士 (bushi, warrior) and 武力 (buryoku, military force). The character evokes strength, arms, and the warrior class.

Together, 建武 can be understood as “establishing martial rule” or “founding of military governance.” The name was chosen to signal a new beginning, one that would combine the authority of the throne with the power of the sword. The irony is that the era ended with the very military force it named being turned against the emperor who had chosen it.

How the Era Name Works

Japanese era names, or nengō (年号), are a system of dating that began in 645 with the Taika reform. Each era name is a two-character phrase, usually drawn from classical Chinese texts, intended to convey a political or moral message. The emperor’s reign is divided into eras, and the era name changes on significant occasions, such as a new emperor’s accession, a natural disaster, or a major political event.

The Kemmu era name was proclaimed in January 1334, after Emperor Go-Daigo had returned to Kyoto and begun his restoration. The choice of 建武 was a deliberate statement of intent: it announced the establishment of a new order, one that would revive imperial authority and, in theory, unify the realm under the throne.

During the Era of Northern and Southern Courts, the system broke down in practice. Two emperors each claimed the right to designate era names, and both used the Kemmu name, but with different end dates. The Northern Court, backed by the Ashikaga shogunate, continued the era until August 1338. The Southern Court, under Go-Daigo, switched to a new era name, Engen, in February 1336. This dual usage meant that a single date could refer to two different years depending on which court’s calendar one followed.

The era name system remained in continuous use from 645 until 1868, when the Meiji Restoration introduced the practice of a single era name for an entire reign. Today, era names are still used in Japan for official documents, calendars, and imperial events. The Kemmu era is remembered not only for its political turbulence but also as a rare instance where the era name itself became a symbol of the conflict it was meant to resolve.