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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The Siege of Inabayama Castle
The two-week-long siege of Inabayama Castle marked the dramatic climax of Oda Nobunaga’s campaign to assert control over Mino Province and decisively crush the Saitō clan. It was during this operation that Toyotomi Hideyoshi, then known as Kinoshita Tōkichirō, first shone brightly in competition with Nobunaga—emerging as the future heir to Japan’s unification.
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The Siege of Wado Castle
In 1335, the Shiina clan built Uozu Castle as an auxiliary stronghold supporting Matsukura Castle. By 1570, it had fallen under the control of the Uesugi clan, rapidly emerging as a strategic fortress in Etchū Province. For many years, Kawada Nagataka served as its commander.
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The Battle of Norada
The Battle of Norada is a striking example of a clash during the Sengoku Jidai period, when numerical superiority did not always guarantee victory, even in open battle.
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Battles of Kawanakajima
The Battles of Kawanakajima were a series of fierce conflicts during Japan's Sengoku period, waged between Takeda Shingen of Kai Province and Uesugi Kenshin of Echigo Province from 1553 to 1564. These battles centered around the strategic Kawanakajima plain, lying between the Sai and Chikuma rivers in northern Shinano Province, now within Nagano City. The rivalry began when Shingen took control of Shinano, forcing Ogasawara Nagatoki and Murakami Yoshikiyo to seek refuge with Kenshin, prompting repeated clashes.
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Siege of Odawara 1590
The Third Siege of Odawara in 1590 was a pivotal moment in Toyotomi Hideyoshi's efforts to neutralize the Hojo clan as a challenge to his authority. In the months leading up to the siege, the Hojo made significant, hurried improvements to the castle's defenses as Hideyoshi’s intentions became clear. However, despite Hideyoshi's overwhelming force, there was little actual combat during the siege.
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Battle of Tenmokuzan
The Battle of Tenmokuzan in 1582 is remembered as the final stand of the Takeda clan in Japan. This battle marked the last attempt by Takeda Katsuyori to resist Oda Nobunaga's relentless campaign against him. Fleeing from his pursuers, Katsuyori set fire to his fortress at Shinpu Castle and sought refuge in the mountains at Iwadono, a stronghold held by his loyal retainer, Oyamada Nobushige. However, Oyamada betrayed Katsuyori, denying him entry. Left with no other option, Katsuyori committed suicide alongside his wife, while the remnants of his army made a valiant effort to hold off their attackers.
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Battle of Oshu
The Northern Fujiwara clan had governed the Mutsu and Dewa provinces since 1087, maintaining their rule for over a century by 1189. The clan was founded by Fujiwara no Kiyohira, alongside Minamoto no Yoshiie, who established their independence in Hiraizumi, located in present-day Iwate Prefecture. Under Kiyohira, and later his successors Fujiwara no Motohira and Fujiwara no Hidehira, the Northern Fujiwara reached the height of their power in the Tohoku region. They infused the area with Kyoto culture and constructed significant temples, such as Chuson-ji, founded in 1095.
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Battle of Omosu
The 1580 Battle of Omosu (Omosu no Tatakai) was one of many conflicts between the Hojo and Takeda clans during Japan's Sengoku period. What sets this battle apart is its rarity as one of the few naval engagements in pre-modern Japan. The conflict occurred off the coast of the Izu Peninsula, involving the fleets of Hojo Ujimasa, the leader of the Hojo clan, and Takeda Katsuyori, the head of the Takeda clan.
