源氏正統を巡る戦いContesting Genji Lineage Legitimacy

Continuing from the previous article, this time we will explore how the Shogun Ieyasu Tokugawa (徳川家康, 1542-1616), who laid the foundations of the Edo period, creatively remixed both old and new concepts based on his unique understanding of history, ultimately establishing the long-lasting system of the Edo Shogunate.

In yesterday’s article, I discussed the meticulous preparations made by Ieyasu Tokugawa in 1566 when he received the surname “Tokugawa” (徳川) from the Imperial Court. He strategically claimed his lineage, the Matsudaira clan, as the legitimate mainstream of the Minamoto (Genji) lineage (源氏), thus preparing the legitimacy of Tokugawa rule even before establishing the shogunate. Personally, among the Sengoku-era warlords, I see Ieyasu as an exceptionally knowledgeable historian who patiently and calmly assessed situations, ultimately rising to the apex as a uniquely intellectual figure, making him complex yet profoundly fascinating.

But what exactly did Ieyasu see as the “legitimate Minamoto lineage”? And what significance did lineage hold during the chaotic Sengoku period when warlords (daimyo) rose across Japan? By interpreting Ieyasu’s perspective, an intriguing historical narrative emerges. Thus, focusing on the successive shogunates of Kamakura → Muromachi → Edo, we will examine the backdrop that led to the peculiar era in which Japan came to have two simultaneous emperors.

The Kamakura shogunate, established in 1185 by Minamoto no Yoritomo (源頼朝, 1147-1199), marked a turning point in Japanese history as the first warrior-led government, replacing the previous aristocracy-centered politics. This shift significantly strengthened samurai influence. After founding the Kamakura shogunate, Yoritomo implemented the system of “favor and service” (御恩と奉公), based on a master-servant relationship with vassals known as gokenin (御家人). Through this system, warriors received guaranteed territories and land distributions in exchange for military service. This strategy unified the scattered samurai, establishing bureaucratic officials across various regions to enhance local governance, distinctly transforming Japan’s governance from aristocratic rule to a warrior-led political structure. This warrior-centric shogunate system established by Yoritomo, who descended from the Minamoto lineage, would later become a critical source of legitimacy.

However, Yoritomo’s direct lineage (嫡流) ended abruptly after just three generations. The direct lineage proceeded from the first shogun Minamoto no Yoritomo to the second shogun Minamoto no Yoriie (源頼家, 1182-1204), and then to the third shogun Minamoto no Sanetomo (源実朝, 1192-1219). But after Yoriie was politically overthrown and assassinated, his younger brother Sanetomo was also assassinated without heirs, ending this direct line. From a genealogical perspective, this marked the extinction of the “main line of the Minamoto shogun family.” Yoritomo’s lineage was known as the “Kawachi Genji” (河内源氏), whose ancestor was Minamoto no Yoshiie (源義家, 1039-1106), an influential warrior during the mid-Heian period. Yoshiie’s prominence led to the branching of many genealogical lines centered around him, collectively termed “Kawachi Genji,” named after Kawachi Province (河内国), an area around present-day Habikino City in Osaka Prefecture. Yoritomo himself descended directly from Yoshiie through his father Minamoto no Yoshitomo (源義朝, 1123-1160).

The genealogy of Kawachi Genji is notably complicated due to its numerous branches. Among these branches were the Ashikaga clan (足利氏), who later established the Muromachi shogunate, and the Nitta clan (新田氏), from which Ieyasu derived his claimed lineage. These genealogical disputes over Minamoto legitimacy became particularly significant during periods of upheaval.

Once the direct line of the Minamoto shoguns ended after three generations, real power shifted to the Hojo clan (北条氏), who had served as regents. Although the Hojo were unrelated by blood to the Minamoto, figures such as Masako Hojo (北条政子, 1156-1225)—Yoritomo’s wife—and her brother Yoshitoki Hojo (北条義時, 1163-1224) effectively consolidated control over the Kamakura shogunate by advising and manipulating puppet shoguns. Interestingly, subsequent shoguns came from imperial or aristocratic families rather than the Hojo themselves, who deliberately refrained from assuming the position of shogun. They believed governance would remain more stable by holding all practical power behind figurehead rulers. Hence, the Kamakura shogunate was effectively maintained by the Hojo regency, although no Hojo member ever became shogun.

Yet this period witnessed significant instability, as remnants of the traditional aristocratic and imperial court power structure persisted despite being severely weakened, sparking unrest. Within the imperial court, Emperor Go-Toba (後鳥羽上皇, 1180-1239) viewed the rise of samurai power unfavorably and secretly planned the overthrow of the shogunate. At the time, warriors were still considered barbaric and of lower status by the aristocracy, creating tensions that would soon erupt.

Continuing from there, in 1221, Retired Emperor Go-Toba raised an army intending to destroy Yoshitoki Hojo, who effectively held the real power of the shogunate, but he was defeated by the Kamakura Shogunate’s forces united under the behind-the-scenes leadership of Masako Hojo. As a result of this defeat, Go-Toba was exiled and confined to the distant Oki Islands, resulting in a major setback for the imperial court and a substantial shift in the power balance toward the warrior class. Immediately afterward, the Kamakura Shogunate established an oversight institution called the “Rokuhara Tandai” (六波羅探題) in Kyoto to closely monitor the movements of the imperial court. Consequently, the court was henceforth placed under the shogunate’s supervision, a pivotal event where warriors suppressed the imperial institution—an essential historical point continually referenced in later periods, notably during the restoration of imperial authority. This sweeping away of imperial influence allowed the Hojo clan to firmly establish their regency government.

However, an unexpected foreign threat emerged, undermining the credibility of the Kamakura Shogunate. This threat was the so-called Mongol invasions of the late 13th century. These invasions, known as the Genko (元寇), named after the Mongol Empire (“Gen,” 元), occurred in two waves—in 1274 and 1281—when the Mongols twice attempted to invade Japan. The primary battlefield was around Hakata Bay in northern Kyushu. In both instances, the invading Mongol fleets were devastated by sudden typhoon-like storms, forcing their withdrawal and preventing the invasion of Japan. These sudden storms are called “kamikaze” (神風, literally “divine winds”) in Japan. Recent investigations in Hakata Bay have scientifically verified the occurrence of these storms. Having personally seen the traces of these events, I can assure you they are not mere legends.

Though the “kamikaze” was fortuitous for the Kamakura Shogunate, protecting Japan from external threats, these were purely defensive wars that brought no territorial gains and left the shogunate unable to provide adequate rewards to the warriors who had fought. Furthermore, the gokenin who served the shogunate fought at their own expense yet received insufficient compensation, leading many into financial hardship. This pivotal event gradually intensified dissatisfaction among the gokenin towards the shogunate (the Hojo clan), fundamentally undermining the shogunate’s authority.

In an attempt to reverse this declining influence, the shogunate canceled debts owed by the gokenin in 1297, but this measure proved insufficient, failing to resolve underlying discontent. The unrest among the gokenin triggered by the Mongol invasions, combined with the deteriorating shogunate finances, significantly contributed to the decline of the Kamakura Shogunate, severely weakening the governance structure of the influential Hojo clan. Against this backdrop, movements aiming to overthrow the shogunate regained momentum. Prominent among these was Emperor Go-Daigo (後醍醐天皇, 1288-1339), the 96th emperor, who advocated for the restoration of imperial authority. Thus, even after their defeat in 1221, imperial factions secretly continued plotting the overthrow of warrior rule, awaiting the opportune moment.

Then, 110 years after the imperial defeat, Emperor Go-Daigo launched a revolution against the Kamakura Shogunate in 1331, declaring the restoration of imperial power and the shogunate’s overthrow. Although this initial attempt in 1331 failed, resulting in Go-Daigo’s exile and confinement on the Oki Islands, anti-shogunate factions had already begun mobilizing throughout Japan. Consequently, in 1333, Go-Daigo escaped from the Oki Islands through cooperation with these anti-shogunate forces, landing in present-day Tottori Prefecture, where he launched a second uprising.

One key figure responding to Emperor Go-Daigo’s second call to arms was none other than Yoshisada Nitta (新田義貞, 1301-1338), a leading figure in the Nitta branch of the Minamoto (“Nitta Genji,” 新田源氏), from whom Ieyasu Tokugawa would later claim his genealogical legitimacy. Under Yoshisada Nitta’s vigorous offensive, the already weakened Hojo regency collapsed, culminating in the destruction of the Kamakura Shogunate. This event ended approximately 150 years of warrior rule, yet the imperial and aristocratic class lacked the means to permanently suppress the already established warrior power, making this interruption brief. Consequently, warrior rule soon re-emerged with the establishment of the Muromachi Shogunate. Meanwhile, as the Kamakura Shogunate collapsed amidst this turmoil, Emperor Go-Daigo immediately returned to Kyoto and established a new government under direct imperial rule, which would subsequently trigger new complications.

The reason was simple: this new regime explicitly rejected warrior governance in favor of aristocratic policies. Personally, I find Emperor Go-Daigo and the nobles around him astonishingly anachronistic, proving clearly they had utterly misread the era. Naturally, this approach heightened dissatisfaction among the warrior class. Additionally, the traditional imperial-aristocratic disdain for warriors manifested in inadequate rewards for the samurai who had contributed to the downfall of the shogunate, along with a pushback against reforms. Consequently, Emperor Go-Daigo quickly lost support among the warriors, creating internal discord within his regime. Ultimately, this discord culminated in 1334 with the defection of Takauji Ashikaga (足利尊氏, 1305-1358), the single most influential figure among the samurai, marking a decisive turning point.

Takauji Ashikaga, previously a prominent gokenin and influential general under the Kamakura shogunate, had become deeply dissatisfied with his treatment. Consequently, starting in 1335, he raised his own banner of rebellion, advocating for the restoration of warrior-led governance. The momentum of history was firmly behind the samurai. Emperor Go-Daigo and his aristocrats, completely out of touch with the times, had no real chance of victory. Within about two years, Go-Daigo’s regime collapsed, and power shifted once again into the hands of the warriors. This transition ultimately culminated in the establishment of the Muromachi Shogunate in 1338. However, just before this, in 1336, Takauji Ashikaga had already placed Emperor Komyo (光明天皇) on the throne in Kyoto, directly challenging Emperor Go-Daigo’s authority. This event plunged Japan into a complicated and contentious era centered around the legitimacy of the imperial throne, with rival imperial factions—each backed by powerful warrior clans—locked in intense power struggles.

This complex and peculiar period, known historically as the Nanboku-cho (Northern and Southern Courts) era, was characterized by the simultaneous existence of two emperors. It was precisely this intricate era of contention over imperial legitimacy that evolved into the disputes over the “authentic Genji lineage” later recognized and strategically utilized by Ieyasu Tokugawa during the Sengoku period.