The Siege of Odawara Castle occurred from the eighth month of Eiroku 3 (1560) to the sixth month of Eiroku 4 (1561) in Kōzuke, Musashi, and Sagami provinces.  More than the siege, this was comprised of a series of battles between the Gohōjō clan and the allied forces of the Uesugi and Nagao clans.  This conflict is also referred to as the Battle of Ōtsuki and served as the opening chapter for an expedition in the Kantō by Uesugi Kenshin that continued for over ten years.  In addition to this event, the Hōjō were later subject to sieges at Odawara Castle by the Takeda in 1569 and by the Toyotomi during the Conquest of Odawara in 1590.  The fact that Odawara Castle was subject to several sieges is reflected in the date noted with the title in Japanese.

On 1/21 of Kyōroku 3 (1530), Uesugi Kenshin was born as the fourth son of Nagao Tamekage, a deputy military governor of Echigo serving the Uesugi family.  His childhood name was Nagao Torachiyo.  On 8/15 of Tenbun 12 (1543), at his coming-of-age ceremony, he adopted the name of Nagao Kagetora.  On 3/16 of Eiroku 4 (1561) when he succeeded to the position of the Kantō kanrei, or deputy shōgun of the Kantō, he adopted the name of Uesugi Masatora.   In the twelfth month of 1561, after this expedition to the Kantō, he received one of the characters from the name of Ashikaga Yoshiteru and changed his name to Uesugi Terutora.  Finally, in the twelfth month of 1570, he adopted the Buddhist name of Fushikian Kenshin, and, thereafter, was referred to as Kenshin.  For historical accuracy, this account reflects the changes to his name over time.

Prelude

In 1546, at the Siege of Kawagoe Castle, Uesugi Norimasa (the fifteenth head of the Yamanouchi-Uesugi family and deputy shōgun of the Kantō) incurred a major defeat with the loss of over 3,000 commanders and soldiers to Hōjō Ujiyasu, fleeing to his base at Hirai Castle in Kōzuke.  Thereafter, he endured continued pressure from the Gohōjō of Sagami.  Witnessing a gradual decline of power, he inferred from Musashi the broader situation in northern Kantō.  In a bid to oppose the Gohōjō, Norimasa entered into an alliance with Murakami Yoshikiyo of Shinano Province, but this forced him into a confrontation with the Kai-Takeda clan who aimed to invade Shinano.  A subsequent defeat at the Battle of Otaihara threatened his main base at Hirai Castle.  He then turned for support to Nagao Kagetora (later Uesugi Kenshin) of Echigo Province.  In 1559, Kagetora went to Kyōto.  While in the capital, he met with Emperor Ōgimachi as well as Ashikaga Yoshiteru (the thirteenth shōgun of the Muromachi bakufu) and exchanged written pledges sealed in blood with Konoe Sakitsugu (later Konoe Sakihisa, the kanpaku, or Chief Advisor to the Emperor).  In a bid to support the deputy shōgun of the Kantō, he then made plans to eliminate the Gohōjō clan.

Assaults on Auxiliary Castles

On 8/26 of Eiroku 3 (1560), based on urgent requests for assistance from Satomi Yoshitaka, Kagetora deployed with over 8,000 troops from Echigo to subdue Hōjō Ujiyasu.  After traversing the Mikuni Pass, early in the tenth month, the Uesugi forces invaded Kōzuke and captured Numata Castle.  While pursuing its lord, Hōjō Ujihide, the Uesugi then toppled Iwashita and Mayabashi castles.  Kagetora seized Mayabashi Castle to use as a base from which to attack the Kantō whereupon he captured Nawa Castle (the base of the Nawa clan) and, after proceeding southward to Musashi, toppled Hanyū Castle.

Meanwhile, Hōjō Ujiyasu laid siege to Kururi Castle defended by Satomi Yoshitaka, but, upon learning of the attacks by the Uesugi army, traveled via Kawagoe Castle and, at the end of the ninth month, entered Matsuyama Castle in Musashi.  Following their former lord, Norimasa, and Konoe Sakitsugu, commanders in Kōzuke and Musashi came together for Kagetora and visibly powerful army.  Meanwhile, the response in Hitachi and Shimotsuke provinces was tepid and, on 9/29, Kagetora requested the Ryūkei Temple to further persuade locals.  He also turned to Ōta Sukemasa to mediate a dispute between Masaki Tokishige (a retainer of the Satomi) and Hara Tanesada (a retainer of the Chiba).  Chiba Tanetomi (the head of the Chiba clan serving as the military governors of Shimōsa and real holder of authority) sent reinforcements to the Hōjō in Koga.  Later, Tanesada later proposed peace negotiations and attended the ceremony for Kagetora to become the deputy shōgun of the Kantō but did not join the Uesugi army.

With the exception of Sagami and Izu, the Hōjō witnessed successive losses of followers in other provinces while demands made upon bushō by Ashikaga Yoshiuji, the Koga kubō and supporter of the Hōjō clan, failed to bear fruit.  The offensive by Kagetora placed Ujiyasu in a vulnerable position, causing him to seek reinforcements from Takeda Shingen to contain the Uesugi from the rear.  Ujiyasu further requested help from the Imagawa clan.  On 5/19 of Eiroku 3 (1560), Imagawa Yoshimoto (a sengoku daimyō and the eleventh head of the Imagawa) died in a lightening attack by Oda Nobunaga at the Battle of Okehazama.  The sudden loss of their lord caused disarray within the Imagawa clan, but his lineal heir, Imagawa Ujizane, dispatched reinforcements to Kawagoe Castle.  The expedition army led by Kagetora, however, did not slow down, and Ujiyasu pulled back from Matsuyama Castle in Musashi, opting to mount a defense from Odawara Castle in Kōzuke.  Early in the twelfth month, the crucial bases at Kawagoe and Sekiyado castles were surrounded by the Uesugi army.  Ashikaga Yoshiuji (the Koga kubō) at Sekiyado Castle, along with Hōjō Ujishige at Tamanawa Castle and Hōjō Ujitaka at Kawagoe Castle all prepared to defend their respective sites.  Meanwhile, Hōjō Ujiteru did not hole-up in Takiyama Castle and instead, in the third month of 1561, went to Taima in Sagami to prepare to intercept the Uesugi forces from Echigo and await reinforcements from the Takeda clan.

In 1561, Kenshin passed the new year in Mayabashi Castle in Kōzuke.  In the second month, Naoe Sanetsuna (later known as Naoe Kagetsuna) was summoned from Echigo to the Kantō.  Kenshin then advanced from Kōzuke and suppressed the Koga palace which was the seat of the Kantō kubō.  By the end of the second month, he arrived at Matsuyama Castle in Musashi Province.  On 2/27, after offering a written prayer for victory at the Tsuruoka-Hachiman Shrine in Kamakura, attacked the coastal area.  The Uesugi forces went via Fujisawa and Hiratsuka to assault Odawara.

Siege of Odawara Castle

In the third month of 1561, assorted bushō from the northern Kantō who were late to join assembled under Kagetora, backing Uesugi Norimasa as the deputy shōgun of the Kantō.  Together with former members of the former Uesugi band of retainers, including Utsunomiya Hirotsuna, Satake Yoshiaki, Oyama Hidetsuna, Satomi Yoshihiro, Oda Ujiharu, Nasu Suketane, Ōta Sukemasa, Mita Tsunahide, and Narita Nagayasu, the expedition army led by Kagetora totaled over 100,000 men.  (Other sources cite a total of (i) over 90,000 men or (ii) 113,000 men.)  After surrounding Odawara Castle and auxiliary castles, the army launched attacks.

On 3/3, the vanguard forces of the Uesugi army set-up a base in Taima and, on 3/8, reached Nakasuji in the Naka District.  On 3/14, the forces collided with a battalion led by Daitō Hidenobu (who supported the Hōjō) at Ōtsuki.  The Uesugi army continued a southward advance with further clashes at Mount Soga on 3/22 and at Mount Nuta on 3/24.  By the end of the third month, Kagetora approached the environs of Odawara and established a base near the Sakawa River.  At Odawara Castle, the main base of the Hōjō that was the focal point of the battle, the battalion led by Ōta Sukemasa stormed the Hasuike gate while the Hōjō forces demonstrated stiff resistance.  Authenticated sources do not include details regarding the siege.  Documents associated with the Uesugi family do not acknowledge a collision between the opposing armies below the castle and merely note that fires were set below the castle to antagonize the defenders, but the Hōjō did not charge out to counterattack the besieging forces.

At the end of the third month, reinforcements from the Takeda clan who allied with the Hōjō arrived in Kai-Yoshida.  Ujiyasu learned that reinforcements from the Imagawa clan had completed preparations to deploy in the next few days.  Around this time, voices of dissatisfaction began to arise among the bushō who had been on the expedition for an extended period.  In Echigo, disputes broke-out over the deployment of soldiers and transport of provisions to the Kantō while Kagetora issued roadside prohibition-edict boards in regard to transport and the horses for transport.

At the beginning of the third month, Kagetora, together with the bushō on deployment, went to Kamakura and held a ceremony for his ascension to the role of deputy shōgun of the Kantō.  He then changed his name from Nagao Kagetora to Uesugi Masatora.  Using this name for only a short period, in the twelfth month of 1561, he changed his name to Uesugi Terutora.

As maternal relatives of the main branch of the Ashikaga, the Uesugi were a family of elevated status and, through this connection, were appointed to serve as the deputy shōgun of the Kantō for generations.  In contrast, the Nagao were of a lineage of retainers of the Uesugi family.  Moreover, the Uesugi family name originated from the Fujiwara clan while the Nagao family name came from the Kanmu-Heishi.  As the deputy shōgun of the Kantō, Masatora headed the Koga kubō and invited Konoe Sakihisa (formerly known as Konoe Sakitsugu) to join his administration.  Discord arose when, among the bushō in the Kantō, Oyama Hidetsuna (a sengoku daimyō and the eighteenth head of the Oyama clan of Shimotsuke) recommended Ashikaga Fujiuji while Yanada Harusuke (a retainer of the Ashikaga) backed Ashikaga Fujimasa.

On 3/16, Kagetora provided a written pledge to Harusuke, making it clear that the allied army backing Fujiuji was not monolithic.  Nevertheless, Kagetora stayed in Yamauchi for several days while consulting with bushō from the Kantō and showing appreciation for the deployment.

To support the Hōjō clan, Takeda Shingen dispatched troops to northern Shinano and, in the fourth or fifth month, toppled Warigatake Castle, an auxiliary site of the Uesugi.  This was a preliminary conflict to the Fourth Battle of Kawanakajima.  The Takeda then completed the construction of Kaizu Castle in Kawanakajima in Shinano.  This posed a threat to Kagetora by enabling the Takeda to continuously observe them at Kawanakajima, forcing Kagetora to devise countermeasures.  Meanwhile, the Takeda instigated an uprising by the Ikkō-ikki in Etchū Province.

At this time, famine occurred across the Kantō so the army struggled to obtain necessary provisions.  Within the ranks of the Uesugi army, Satake Yoshiaki along with members of the Oda and Utsunomiya clans demanded a withdrawal on the grounds that they could not engage in an extended deployment.  Some bushō pulled-up without permission.  Alignment among the troops withered, marked by a revolt by Ueda Tomonao at Matsuyama Castle in Musashi who betrayed the Uesugi in favor of the Hōjō.  In the end, the Uesugi were unable to topple Odawara Castle.  The Hōjō succeeded in keeping their control of auxiliary sites including Tamanawa, Takiyama, Kawagoe, and Edo castles.  Meanwhile, Masatora aimed for a final showdown against Shingen at Kawanakajima and, without heading again toward Odawara Castle, withdrew his forces and departed from Kamakura.

Thereafter, during the return to Echigo, in the fourth month, Masatora captured Matsuyama Castle from Ueda Tomonao and assigned Uesugi Norikatsu to serve as the commander of the castle.  Ashikaga Fujiuij and Konoe Sakihisa were located at the Koga palace.  Masatora received a gonaisho, or personal letter in the form of an official document, from Ashikaga Yoshiteru, the thirteenth shōgun, commending his deployment to the Kantō.  At the end of the sixth month, he departed from Mayabashi Castle and, in the tenth month, ended the expedition to the Kantō.

In addition to the rebellion by Ueda Tomonao during the deployment, after Masatora departed from the Kantō, the Tōgane-Sakai, the Yamamuro, and the Takagi clans reverted to allegiance to the Hōjō clan.

Consequences

By leading an army of over 100,000 soldiers to invade deep into the territory of the Hōjō and holding a ceremony at the Tsuru-Hachiman Shrine in Kamakura to assume the role of deputy shōgun of the Kantō, Uesugi Kenshin became known across the land.  At the same time, after withstanding a month-long siege, Odawara Castle gained recognition as a stronghold although, per recent research, the siege may have been limited to ten days.  In any event, despite the lack of a final resolution, in a relatively short period of time Kenshin was able to corner the Hōjō clan.  After his return to Echigo, the Hōjō regained power.  Thereafter, the two clans continued to engage in fierce battles across the Kantō with the involvement of the Takeda clan.

After the expedition, the alienation of bushō in the Kantō and their reversion to the Hōjō clan was occasioned by pressure from the Hōjō in addition to the dissatisfaction of some bushō with respect to their ranks established by Kenshin in his role as the deputy shōgun of the Kantō.  Prior to the rise of the Hōjō in the Kantō, power struggles caused fractures within the Kantō kubō, as well as the family of the deputy shōgun serving as the officials of the administration, which led, in turn, to conflicts among the bushō in the Kantō.  With the exception of the Satake, the Satomi, and the Ōta who maintained their opposition to the Hōjō, many bushō in the Kantō, amidst the turbulence between the Uesugi and the Hōjō, reverted to the Hōjō whose governance was based in the region or declined as a result of the ongoing struggle between the opposing parties.

Having survived the attacks by the Uesugi and bushō in the Kantō under their command during the expedition, the Hōjō continued construction work at Odawara Castle and expanded their sphere of influence.  During a subsequent attack by Takeda Shingen, the Hōjō continued to successfully defend Odawara Castle.  In 1590, during the Conquest of Odawara by Toyotomi Hideyoshi, the besieging army with 220,000 soldiers including many prominent bushō established a nine-kilometer perimeter encompassing the surrounding fields and town below the castle.  The garrison defended against these forces for three months, denying the Toyotomi army from taking the castle by force.  Nevertheless, after the fall of a series of auxiliary sites, along with collusion by senior retainers from within the castle, based on the persuasive efforts of family members who earlier surrendered along with a faction opposed to the battle, the defenders finally vacated the castle.

According to a popular version of events, the Hōjō decided to fight against the allied forces of the Toyotomi owing to overconfidence stemming from earlier successes defending the castle, which then brought about the decimation of the Hōjō clan.  In fact, at the time that there appeared to be a resolution to the long-contested territory of the Numata in eastern Kōzuke, a decision was made for Hōjō Ujiyasu to travel to Kyōto to participate in the Toyotomi administration.  Meanwhile, the decision to hole-up in the castle resulted from a declaration of war by Hideyoshi in response to the Nagurumi Castle Incident by which, in the eleventh month of 1589, the Hōjō captured the castle from the Sanada.  This unraveled a settlement of the territorial disputes in Kōzuke arranged by Hideyoshi by which the Hōjō were to receive two-thirds of the province and one-third for the Sanada.

Matsudaira Motoyasu

In the fifth month of 1560, at the Battle of Okehazama, a small contingent led by Oda Nobunaga killed Imagawa Yoshimoto while Yoshimoto was attempting to pass-through Owari Province.  In the wake of this event, Matsudaira Motoyasu (later known as Tokugawa Ieyasu) who was under the command of the Imagawa returned to their base at Okazaki Castle in Mikawa Province.  In the fourth month of 1561, he attacked Ushikubo Castle (which was aligned with the Imagawa), rebelled against the Imagawa and achieved independence.  He then entered into an alliance with Oda Nobunaga.  There is a view that these developments in Mikawa were a factor in the decision of Kenshin to launch an assault against the Hōjō at Odawara Castle.

Regarding his steps to become independent of the Imagawa clan, Motoyasu was concerned of potential support for Ujizane from the Takeda and Hōjō clans.   Kenshin’s invasion of the Kantō, however, compelled the Takeda and Hōjō to confront the Uesugi, eliminating their ability to send reinforcements to Mikawa on behalf of the Imagawa and thereby facilitating Motoyasu’s actions.  Meanwhile, in the immediate aftermath of the Battle of Okehazama, Motoyasu may not have been weighing the prospect of his own independence and, instead, obeyed orders from Ujizane to make preparations at Okazaki Castle in the event of an invasion of western Mikawa by the Oda army.  Subsequently, Motoyasu became disenchanted after Ujizane sent reinforcements to Odawara Castle in support of the Hōjō instead of receiving troops in Mikawa from the Takeda and the Hōjō.  Rather than fight against the Oda without support, he therefore aimed to maintain his territory in western Mikawa by allying with the Oda and becoming independent of the Imagawa.

Later, Imagawa Ujizane dispatched messengers to the Hōjō and Takeda clans to urgently request reinforcements to reclaim Mikawa.  Shingen issued directions to the Shimojō clan, kunishū, or provincial landowners in southern Shinano, to conduct covert solicitations of targets in Mikawa, but, in 1563, after a large-scale revolt erupted among the kunishū in Tōtōmi Province, Ujizane’s powers of governance were called into question, prompting Shingen to cut ties with the Imagawa and investigate whether to invade their territory instead.

Anecdotes

In one story, around noon on one day during the siege of Odawara Castle, Kenshin tethered his horse on the edge of a lotus pond, opened a boxed lunch that he had carried with him, and began to enjoy his lunch within sight of the castle.  After spotting him, ten soldiers from an arquebus unit of the Hōjō army aimed at Kenshin and fired two rounds each, but the bullets did not pierce the armor on his sleeves and he contentedly continued his meal while drinking three cups of tea.

In Kamakura, during the ceremony for Kenshin to become the deputy shōgun of the Kantō some of the bushō bowed down to pay their respects. Narita Nagayasu, having come from a prominent family descended from the Fujiwara clan, paid his respects from atop his horse.  Unaware that this was his custom, Kenshin regarded the act as disrespectful and thrashed Nagayasu in the face with his folding fan.  After the encounter, Nagayasu withdrew his soldiers to his base.  Later, this incident is said to have been a catalyst for other bushō in the Kantō to revolt, but this thrashing of Nagayasu is not recognized as fact among scholars.  He is said to have come into conflict with Kenshin in regard to the return of the Hanyū territory in Musashi.

According to another account, at the ceremony for Kenshin to become the deputy shōgun of the Kantō, Chiba Tanetomi and Oyama Takatomo argued over the seating order.  Following mediation by Kenshin, the two initially settled and took their seats, but, soon thereafter, Ōishi Genemon withdrew from the group and, after returning to his own territory, Tanetomi agreed to rejoin the Hōjō clan.  Owing to these developments, Takatomo, in addition to the Isshiki, the Yūki, the Naganuma, the Mibu, the Moro, and the Sōma clans pulled back their troops.