In Japanese history, the siege of Ishiyama Hongan-ji — the main stronghold of the Ikkō-ikki movement during Oda Nobunaga’s campaign — is considered the longest, lasting from August 1570 to August 1580.
Initially, in 1496, the monk Rennyo (1415–1499), the ideological and spiritual leader of the Jōdo Shinshū Buddhist sect, withdrew to the mouth of the Yodo River and built a secluded hermitage on the ruins of the ancient Naniwa palace, on the "great slope" — Osaka. This modest retreat quickly grew into a large temple complex, and by 1532, after the destruction of Yamashina Mido, Ishiyama Hongan-ji had become the central fortress-monastery of the Ikkō-ikki, surrounded by the temple town (jinai-machi).
The monastery’s defenses were superbly designed: located on islands at the river’s mouth, surrounded by natural moats (channels) with bridges that could be quickly dismantled in case of attack. Defensive features included earthen ramparts (dorui) with palisades, moats (hori), Koraimon-style gates, and watchtowers. The surrounding jinai-machi acted as the outer perimeter, divided into wards by earthen walls (dobei) and moats. At the center was the island core, fortified with stone walls (ishigaki), dobei, yagura towers, and heavy yaguramon gates—closely resembling a fortified samurai castle.
Instead of a donjon, the central area housed two main halls—Amidado and Goeido—connected by a corridor. These architectural forms remain in use in modern Jōdo Shinshū temples.
The standing garrison consisted of about 100 monks, but at the toll of a bell, up to 10,000 lay followers (monto), including those from Kaga and Echizen provinces, could be summoned. The Mori clan’s navy actively supported the monastery, while Uesugi Kenshin and Takeda Shingen diverted Nobunaga’s forces in the northwest, slowing the siege.
In August 1570, Nobunaga, with a force of around 30,000, initiated the siege, surrounding the monastery with forts. In September, warrior-monks stormed the Kawaguchi and Takadono forts using 3,000 arquebusiers and coordinated volley fire.
The first years were intense, but sea routes kept the monastery supplied until 1576–1578, when Nobunaga shifted focus to maritime blockade using large ships and arquebusiers. After victories in the second Battle of Kizugawaguchi and the death of Uesugi Kenshin, Nobunaga entered the final phase: cutting off allies and capturing outer defenses.
In April 1580, abbot Kōsa (Kennyo) surrendered under imperial order, but the monastery was burned to prevent its capture. Its foundations were destroyed in August. Three years later, in 1583, Toyotomi Hideyoshi built Osaka Castle on the site.
Thus, the siege of Ishiyama Hongan-ji became the largest and longest fortress war in Japanese history, showcasing the defenders' caution and the besiegers’ persistence.
See also
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First Battle of Azukizaka
In response to the Oda clan's advance into the western part of Mikawa Province, in August 1542, the combined forces of Imagawa Yoshimoto and Matsudaira Hirotada (father of the future shogun Tokugawa Ieyasu) advanced into the Ikutahara area.
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Battle of Ankokuji
As a result of the summer campaign of 1542, the Suwa clan was completely defeated. Takeda Shingen stationed his military contingent at Uehara Castle. Takeda's army general, Itagaki Nobukata, subsequently became the commandant of this castle.
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The Siege of Matsuyama Castle
In 1537, the head of the Ogigayatsu branch of the Uesugi clan, Uesugi Tomooki, died. He was succeeded by his son, the thirteen-year-old Uesugi Tomosada (1525–1546). Hojo Ujitsuna (1487–1541), who had long been planning to expand his holdings in Musashi Province, decided to take advantage of the new daimyo's inexperience. He assembled an army of 7,000 soldiers and marched on Kawagoe Castle.
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The Siege of Unokuchi Castle
One of the important steps in the career of every Japanese commander was the uijin, the first military campaign in which he took part. For the legendary Takeda Shingen, according to some sources, this campaign was the siege of Unokuchi Castle.
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Battle of Arita-Nakai
By 1517, Takeda Motoshige, lord of Kanyama Castle, was probably the most influential daimyo in Aki Province. Ten years earlier, he had served as a vassal of the Ōuchi clan and participated in Ōuchi Yoshiyuki's campaign in Kyoto. This campaign was part of an effort to support the deposed shogun Ashikaga Yoshitane.
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The Siege of Arai Castle
Hojo Nagauji (Soun) (1432–1519) went down in Japanese history as one of the most notable figures of his time. He is considered a prime example of a gokoku-jo daimyo. The process of gokoku-jo literally means “the lower classes defeat the upper classes” and in Japanese history was expressed, among other things, in the elevation of minor samurai to the status of owners of entire provinces.
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Battle of Sakai
Ōuchi Yoshihiro was an influential shugo of the provinces of Suō and Nagato and played an important role as a supporter of the Ashikaga clan during the war with the Southern Court. His greatest achievement was forcing the Southern Court emperor to surrender in 1392, which brought an end to the Nanboku-chō period. This victory strengthened the Ashikaga clan's position and marked the end of the long-standing rivalry between the two imperial lines.
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Battle of Shijonawate
After Kusunoki Masashige's death in the Battle of Minatogawa, his son, Kusunoki Masatsura, continued his work supporting the Southern Imperial Court in the Nanboku-chō period war. He took on his father's legacy not only as a duty, but also as a way to remain faithful to the ideals for which Masashige had given his life.
