Oda Nobunaga, the legendary leader of the Oda clan, led his forces – alongside the Matsudaira clan – to Kyoto, across Honshu, and towards the unification of Japan. Known for his tactical brilliance and leadership, Nobunaga is rightly remembered as one of Japan’s most revered leaders. He defeated even the most respected and powerful clans in the country, such as the Uesugi and Takeda. His right-hand man, Tokugawa Ieyasu, was said to have convinced the army of Takeda Shingen’s son – whose father had pioneered the cavalry charge in Japan – to surrender with only five men and a handful of shinobi.
Most would assume that only the samurai, who Nobunaga’s armies were cutting down by the thousands, could match his strength. Yet they would be mistaken. Nobunaga’s true threat did not come from disciplined samurai bound by Bushidō and the will of their daimyō, but from an unorganised force of militant Buddhists.
The first instances of peasant revolt movements in Japan appeared in the 14th century. However, the Ikkō-ikki only became truly unified – though still dispersed – in the aftermath of the Ōnin War in 1477. The alliance stemmed from an aggressive sect of Buddhism known as Jōdo Shinshū, which taught that enlightenment could only be achieved through absolute faith. Though the Ikkō-ikki had roots in economic unrest, their identity became inseparable from Jōdo Shinshū. Their name, meaning “single-minded league”, referred to their shared belief in salvation through the Pure Land – Amitābha in Sanskrit, Amida in Japanese.
The group originally formed around the followers of the priest Rennyo, who fled persecution from the Hongan-ji temple in Kyoto. Over time, his followers grew in number and conquered Kaga Province, forming Japan’s first peasant-ruled religious domain. The sect spread across Honshu, drawing in priests, peasants, and merchants alike. Rennyo stepped down as patriarch in 1489 and died in 1499 – but the movement did not end with him.
The following year, Rennyo’s second son, Jitsunyo, took control of the Hongan-ji. His early rule was cautious and conservative, consolidating land and followers. But with the outbreak of the Sengoku Jidai – the Age of Warring States – indecision meant death. When a coup shook the Ashikaga shogunate, the deposed deputy shogun Hosokawa Masamoto conscripted the Hongan-ji to his cause. Jitsunyo initially refused, but Masamoto forced his hand, creating a schism within the Ikkō-ikki. When the conflict ended with Masamoto’s death, Jitsunyo reorganised the sect, distinguishing between temples fully within the Ikki and those merely subordinate to it.
In 1525, after Jitsunyo’s death, his successor Shōnyo constructed an immense fortress complex at Ishiyama Hongan-ji, just outside Kyoto, and began establishing temples across the Mikawa region. This expansion, however, would prove to be one of the Ikki’s fatal mistakes. Matsudaira Takechiyo – later known as Tokugawa Ieyasu – noticed their growing presence in his home province. In 1564, as Ieyasu and Nobunaga began their campaign to unify Japan, Ieyasu crushed the Ikkō-ikki of Mikawa at Azukizawa, forcing them to flee.
In the years that followed, Nobunaga seized Kyoto, defeating the Azai, Saitō, and Asakura clans with the support of the shogun Ashikaga Yoshiaki. However, when Yoshiaki realised Nobunaga intended to use him as a puppet, he turned to the Ikkō-ikki for aid. This was especially problematic for Nobunaga, as Ishiyama Hongan-ji sat in a key strategic position between Kyoto and Osaka. Yet the Ikki proved far more difficult to fight than expected.
First, they were not bound to specific territories and could appear anywhere within Nobunaga’s domain. Second, unlike the samurai, they did not follow the Bushidō code and freely used firearms – weapons still considered taboo by many warriors. Third, they were supported by Nobunaga’s former enemies, the Azai and Asakura clans, now recovered and in truce with him. And finally, they retained control of their mighty fortress, Ishiyama Hongan-ji – a name Nobunaga would come to loathe.
After securing peace with the Azai and Asakura, Nobunaga turned his attention to the Ikki strongholds: Ishiyama Hongan-ji and the fortress at Nagashima. Nagashima fell after four years, but Ishiyama Hongan-ji endured. For eleven long years – nearly the entirety of Nobunaga’s campaigns – the fortress held. The siege became known as the Ishiyama Hongan-ji War. In 1580, the fortress finally fell. Surprisingly, due to the emperor’s intervention, the monks were spared, though the Hongan-ji itself was burned to the ground.
Later, when Nobunaga attacked another monastery at Mount Hiei – ironically, the birthplace of Jōdo Shinshū – he showed no mercy. The entire population, estimated between 4,000 and 20,000 people, was executed, regardless of whether they were combatants. Thus ended the Ikkō-ikki, another fallen power crushed on the bloody path of Nobunaga, Hideyoshi, and Ieyasu. The ruins of Ishiyama Hongan-ji would later serve as the foundation for Toyotomi Hideyoshi’s now-famous Osaka Castle.
In conclusion, while the Ikkō-ikki might appear to be just another of Nobunaga’s many enemies, they were far more than that – a force of remarkable spirit and determination. This loosely bound league of priests, merchants, and peasants, who conquered a province, stood as the greatest obstacle to Nobunaga’s unification of Japan.