Following the death of Nobuhide in 1552, former disloyal bushō of Nobuhide in Owari took up arms. Nobunaga soon found himself in the midst of a struggle for control of the province. All together, the conquest of Nobunaga’s home province of Owari took about seven years – until 1559. During this period, Nobunaga engaged in no less than twelve battles, wiped out opposition from both branches of the Oda clan, warded off advances by the Imagawa into Owari, and secured his position for the next major phase of his conquest.
Nobunaga did not aim for a decisive victory over the Imagawa. He knew that if he went too far, Yoshimoto would send a large contingent into Owari, and Nobunaga did not have sufficient resources to defeat the Imagawa at the time. He needed to show that he would take a stand to defend the territory in his home province, but not threaten neighboring provinces.
In addition to the threat posed by Nobuhide’s surviving bushō, Nobunaga confronted a challenge from his brother, Nobukatsu, to his position as the designated heir to the Oda clan. This looming conflict within the clan compelled retainers to take stock of their own security. Yamaguchi Noritsugu, lord of Narumi Castle and a dogō in the Kasadera District of Owari, and his son, Noriyoshi, defected to the Imagawa, resulting in the loss of Narumi Castle in a contested border area between Owari and Suruga. The internal divisions following Nobuhide’s death, and the steady advance of Yoshimoto into eastern Owari, had convinced Noritsugu to bet on the Imagawa as the victors in an eventual confrontation. Noritsugu assigned Noriyoshi to stay at Narumi while he fortified his defenses at Sakuranakamura Fort with the support of the Imagawa. Meanwhile, the lord of Tobe Castle in the same region also switched allegiance to the Imagawa. As a result, the Imagawa gained further influence along the tense border.
Thereafter, Nobunaga led eight hundred men toward Narumi Castle, setting up camp nearby at Sannoyama. Noriyoshi responded by departing the castle in command of one thousand five hundred men, including troops from the Imagawa. He encountered Nobunaga’s forces to the northwest of Narumi in Akatsuka in the spring of 1552. A fierce battle ensued; the soldiers clashed with spears and pulled opponents off their horses in close combat. Some of the adversaries knew one another because the Yamaguchi had until then supported the Oda, but they fought aggressively anyway. This battle marked the outbreak of opposition within Owari to Nobuhide’s former stronghold, ending with no decisive victor. After the battle, the two sides exchanged captive men and horses and withdrew, but Nobunaga had lost thirty members of his cavalry. The loss of Narumi to the Imagawa particularly troubled Nobunaga owing to its strategic position alongside Ise Bay where the tide flowed to the base of the castle. Narumi stood up the coastline from Ōdaka Castle, together forming a strategic line from which to control access to the sea and the Tōkaidō route. Yoshimoto later assigned Okabe Motonobu, a loyal bushō, to defend Narumi. Before long, Yoshimoto summoned Noriyoshi and Noritsugu to Suruga, and upon his orders, had both of them commit seppuku.
Oda Nobutomo was the heir of Oda Michikatsu, a shugodai and lord of Kiyosu Castle who led the Yamato-no-kami branch of the Oda clan and governed the four southern districts of Owari. He served under Shiba Yoshimune, the nominal shugo in Owari, who preferred to indulge in kabuki and musical arts rather than serious matters of governance. On his part, Nobutomo also showed little interest in policy matters. Despite opposing Nobuhide as leader of their primary rival, Nobutomo’s inaction enabled the Ise-no-kami branch from which Nobunaga ascended to consolidate more political and economic power in Owari under Nobuhide. Ambitious retainers such as the Sakai and the Kawajiri clans posed a further challenge to Nobutomo’s governance of the province.
After Nobuhide’s death, Nobutomo boldly announced to his retainers, as well as to Oda Nobuyasu of the Ise-no-kami clan, that he would assume leadership of the entire Oda family. In so doing, he would allow Yoshimune to reside at his base in Kiyosu Castle. Yoshimune began to resent the manipulation by Nobutomo, causing a rift between the men. Beyond issues of authority, their mutual interest in one of Nobuhide’s former mistresses, Iwamuro, only served to deepen their differences. Yoshimune could not content himself with presiding over affairs absent any real authority.
Nobutomo allied himself with Oda Nobukatsu in an effort to defeat Nobunaga. After the defection of Yamaguchi Noritsugu at Narumi Castle, he collaborated with Sakai Daizen, a magistrate to the military commissioners at Kiyosu. These men saw the power vacuum left by Nobuhide as a rare opportunity to expand their influence beyond the southern portion of Owari and to outmaneuver the Ise-no-kami clan. Daizen had posed a threat to Nobunaga ever since his earlier rebellion against Nobuhide in the autumn of 1548, which, although peacefully resolved through the offices of Masahide, evidenced his personal ambitions.
In 1552, Daizen attacked and captured the castles of Matsuba and Fukada, taking hostage their lords, Oda Iganokami and Oda Nobutsugu, who supported the Ise-no-kami. Nobunaga departed Nagoya Castle to mount counterattacks on the seized castles and to advance on Nobutomo’s base at Kiyosu. Nobumitsu, Nobunaga’s uncle and lord of Moriyama Castle, joined forces with Nobunaga. Together, their troops crossed the Shōnai River, advancing to Kayazu, located four kilometers to the south of Kiyosu. In the early morning, the combined forces clashed in the fields of Kayazu with a contingent headed by a senior retainer named Sakai Jinsuke. Chūjō Ietada and Shibata Katsuie soon killed Jinsuke and fifty men under his command, and then recaptured both castles. This weakened support for Nobutomo, and demonstrated that Nobunaga could succeed in combat in the wake of the loss of Nobuhide.
Yoshimune, together with retainers Yanada Yajiemon and Nagoya Yagorō, thwarted a later plan by Nobutomo to assassinate Nobunaga, and encouraged elders at Kiyosu Castle to support Nobunaga. Upon learning of these plans, Nobunaga and his men headed toward Kiyosu to set fires to the surrounding town, but did not attempt an assault on the firmly protected castle. Nobutomo became enraged after hearing that Yoshimune had secretly confided in Nobunaga of his plans. In 1554, Nobutomo and Daizen launched a coup de état against Yoshimune. On the fateful day, Yoshimune’s lineal heir, Yoshikane, led many of the young and capable retainers out of Kiyosu Castle to fish with nets on a nearby river. Nobutomo and Daizen seized that moment to attack Yoshimune in his quarters at the castle while defended by mostly elder retainers. Scores of defenders perished. Yoshimune took his own life while Yoshikane escaped to the custody of Nobunaga at Nagoya Castle. This turn of events abruptly ended Yoshimune’s role as shugo of Owari after just one year.
Nobunaga used this opportunity to plan an attack on Kiyosu Castle, ordering Shibata Katsuie, a retainer of Oda Nobukatsu, to do so within one week of the take over. Forces departed Kiyosu Castle to confront the attackers, but Katsuie and his men defeated them at Sannokuchi, causing them to retreat toward Seigan Temple in the Ajiki District in the northern part of Nagoya. Some commanders, including Kawajiri Yoichi, Oda Sanmi, and over thirty elite members of the cavalry from the Kiyosu faction died in battle, overpowered by the longer spears wielded by Katsuie’s men.
Having suffered losses in the Battle of Ajiki, Daizen conceived a plan to regain his high stature by reaching out to Nobumitsu, encouraging him to join a conspiracy against Nobunaga. Nobumitsu had earlier been recognized by Nobuhide for bravery as one of a group of seven spear-wielding combatants in the First Battle of Azukizaka. Daizen proposed to Nobumitsu that he enter Kiyosu Castle in the role of a shugodai, sharing responsibilities with Nobutomo. Nobumitsu pledged cooperation, but, unbeknown to Daizen, Nobumitsu had devised his own plot to ensnare him. Apart from his blood ties, Nobumitsu weighed the balance of power and chose his sides. He had already agreed to a plan with Nobunaga to divide control over the four southern districts of Owari, as separated by the Shōnai River.
In 1554, Nobumitsu entered Kiyosu Castle and prepared to assume his quarters in the south tower. Sensing danger, Daizen unexpectedly fled for his life to Suruga Province to seek protection from the Imagawa. Nobumitsu soon confronted Nobutomo to settle accounts for having slayed Yoshimune. Out of options, Nobutomo took his own life. The trap that he thought he had set for Nobunaga reversed on him. As promised, Nobumitsu turned control of Kiyosu Castle over to Nobunaga and, in exchange, moved to Nagoya Castle. The strategy to outwit the lords of the Kiyosu faction had succeeded.
Yoshikane’s appeal for protection allowed Nobunaga to capitalize upon the revenge earlier taken by Nobutomo against Yoshimune. Nobunaga viewed Nobutomo as a nominal retainer who had failed to obey him despite having a subservient relationship. Nobutomo’s slaying of Yoshimune provided Nobunaga the pretext to bury him as a relatively unknown assassin of the head of the shugo family that formerly governed the Oda, and avoid the notoriety of such an act himself.
Nobunaga assigned Yoshikane the title of shugo and tasked him with forging an alliance among all clans obedient to the Ashikaga, including the Kira of Mikawa and the Imagawa of Suruga. While Yoshikane met with Kira Yoshiaki in Toda to negotiate who among the highest-ranking members of the clans would have superiority, the Shiba and Kira forces solemnly awaited the outcome at Uenohara. Neither side compromised, so the meeting ended with the sides taking ten steps forward to peer at their counterparts, dispensing with customary formalities.
Despite this initial controversy, Yoshikane conspired with Yoshiaki in a bid to banish Nobunaga and to restore the authority of the Shiba clan associated with a shugo title. Nobunaga heard these rumors that Yoshikane and Yoshiaki had secretly collaborated with the Imagawa through the devices of Hattori Tomosada, an adherent of the Ikkō sect from a wealthy family in the Kawachi District south of Tsushima. The plan called for hailing Imagawa forces by a sea route to attack the Oda. Nobunaga then banished Yoshikane from Owari, marking the end of the Shiba clan as a daimyō. Tomosada managed to remain independent of the Oda based on his cooperative ties to the Ganshō Temple which governed the monks from the Hongan Temple in the Tōkai Region.
Nobunaga’s move to Kiyosu Castle served at least two important ends: first, it marked his command of the traditional headquarters of the Oda clan at the center of Owari, and, second, it offered a strategic location. Since the late fifteenth century, Kiyosu had been the base for the supreme military commissioner in Owari. The castle resided on a natural dam traversed by the Gojō River that served as an important shipping lane. This led to the growth of a town on the expansive Nobi Plain surrounding the castle. Prior to Nobunaga’s arrival, the town of Kiyosu had already developed into the political and economic center of Owari. Nobunaga thereby followed the pattern originally set by Nobuhide to fortify his position by relocating his headquarters. After major renovations, Nobunaga moved in and retained Kiyosu as his home base for almost ten years.
Less than one year after assuming his position as lord of Nagoya Castle, in 1556, Nobumitsu unexpectedly died at the hands of his retainers. Nobunaga may have instigated the act in connection with a promise regarding the division of the four southern districts of Owari, but the motives are unclear. Hayashi Hidesada, a former retainer of Nobuhide, succeeded Nobumitsu as the lord of Nagoya Castle.
In 1557, Oda Nobuhiro, a half-brother of Nobunaga, planned an attack on Nobunaga at Kiyosu Castle. Nobuhiro had colluded with Saitō Yoshitatsu, and led them into Owari. Believing that Nobunaga would set out to counter the Saitō, Nobuhiro plotted to dispatch troops under the guise of supporting Nobunaga, and then to capture Kiyosu Castle while Nobunaga was away in battle. Even if Nobunaga attempted to return, Nobuhiro intended that Nobunaga would be caught in-between the insurgents and the invaders from east to west. Before departing, Nobunaga had locked down Nagoya Castle and issued strict orders to prohibit all visitors. The Saitō eagerly awaited news that Nobuhiro had captured the castle. Instead, his troops could not enter the castle and the plan failed. Nobuhiro surrendered and denounced his plan with the Saitō. He received a pardon, and served under Nobunaga for many years thereafter. Meanwhile, having lost the support of Nobuhiro, the Saitō retreated from Owari to Mino Province.
The Iwakura branch of the Oda clan controlled the four northern districts of Owari from their base at the original home of the clan. Like their brethren from the Kiyosu branch, the Iwakura embarked on an outright attempt to defeat Nobunaga.
Although originating from the Yamato-no-kami clan, Oda Nobuyasu (信安) served as lord of the Ise-no-kami faction at Iwakura Castle. After the death of his father, Toshinobu, Nobuyasu had been too young to take control of Iwakura, so he received the support of Oda Nobuyasu (信康), a younger brother of Nobuhide based at Inuyama Castle. Nobuyasu (信安) married a younger sister of Nobuhide, and owing to these ties, had been on friendly terms with Nobunaga as cousins, engaging with him in the traditional dramatic art of sarugaku. After Nobuhide’s death, Nobuyasu (信安) disputed over territory with Oda Nobukiyo, the eldest son of Nobuyasu (信康), alienating himself from Nobunaga in the process.
In 1553, he came to believe in a rumor that Inada Sadasuke, an elder in his clan, had been colluding with Nobunaga, thereby ordering him to commit seppuku. The Inada had served the shugodai of the Oda clan in the northern districts of Owari for generations. His third son, Tanemoto, was sheltered at the age of nine by Sadasuke’s friend, Hachisuka Masakatsu. Sadasuke came to know Masakatsu in the course of battles in Owari and in cooperation with the dogō located in the environs of the Kiso River between Owari and Mino provinces, for which he proved himself to be a trusted partner.
In 1556, Nobuyasu (信安) joined forces with Saitō Yoshitatsu in opposition to Nobunaga after Yoshitatsu defeated his father, Dōsan, in the Battle at Nagara River in neighboring Mino Province. In the same year, Nobuyasu allied himself with Nobunaga’s younger brother, Nobukatsu, lord of Suemori Castle, at the Battle of Inō against Nobunaga. As an alternate account, Nobuyasu contemplated a settlement with Nobunaga, but his second son, Nobukata, joined forces with Saitō Yoshitatsu and Oda Nobukatsu, remaining hostile despite his lineal ties to the bugyō who served the shugodai in the southern districts of Owari.
Nobuyasu (信安) favored his second son, Nobuie, to serve as his successor, rather than his first son, Nobukata. This led Nobukata to collaborate with Inada Shirinojō in 1557, banishing his father and brother from Iwakura and seizing control of the castle. Nobuyasu then became a retainer of Saitō Yoshitatsu, and after Yoshitatsu’s death, served his son Yoshikoki in a failed resistance to Nobunaga. Once the Saitō clan finally collapsed, Nobuyasu fled to Kyōto. Fortunately for Nobuyasu, Nobunaga forgave his transgressions out of familial loyalty, assigning him a small fiefdom in the town of Shirogane in Mino. Later, he served as an administrator at Azuchi Castle. His son, Nobuie, became a retainer of Nobunaga’s eldest son, Nobutada.
Nobunaga viewed this internecine struggle as an opportunity to overthrow the whole faction, and, together with troops sent by Nobukiyo, attacked Nobukata in Ukino in 1558. The forces were about equal in number, with Nobunaga leading two thousand of his own men plus one thousand sent by Nobukiyo against the three thousand forces of Nobukata. The battle erupted around noon, and fierce fighting ensued.
Skillful use of the arquebus and the bow by Nobunaga’s forces resulted in defeat for Nobukata and his men. Mori Yoshinari and Chūjō Shōichiro fought valiantly for Nobunaga, driving Nobukata’s men back to the perimeter of their castle. Nobunaga’s troops split from the support troops, and roundly defeated the enemy, who launched a desperate counterattack with their remaining forces. The head count held the following day at Kiyosu Castle totaled one thousand two hundred fifty men – nearly half of Nobukata’s forces. This marked an important victory for Nobunaga on the path toward eliminating all of his opponents within the Oda clan.
The bitter defeat at Ukino undermined Nobukata’s position, leaving him with the unenviable choice of fleeing or fighting to the death in an attempt to hold on to Iwakura castle. In the following year, Nobunaga toppled Iwakura Castle, burning it to the ground and ending the governance of the Ise-no-kami faction of the Oda clan that had endured since 1478. Nobukata’s attempt to hold-out for several months in the castle had failed and he was banished. Nobukiyo joined Nobunaga in this attack. The demise of the Ise-no-kami prevented Nobuyasu from returning to Owari to challenge Nobunaga. Some former retainers of Nobuyasu, such as Yamauchi Katsutoyo, eventually joined in support of Nobunaga in the aftermath of this contest for control of the clan and the province.
While it appeared that Nobunaga had finally unified Owari, Nobukiyo contested Nobunaga’s proposed division of Nobukata’s former territory. Nobukiyo was based at Inuyama Castle. Constructed on a hill alongside the Kiso River, Nobuyasu (Nobunaga’s uncle) had first moved to Inuyama in 1537 after abandoning Kinoshita Castle. Nobukiyo inherited the castle in 1544 following the death of his father in battle with Saitō Dōsan in 1542. At the time, Nobuyasu joined Nobuhide in the attack on Dōsan, torching the villages that lay below Inokuchi Castle on Mount Inaba. Dōsan then caught Nobuyasu off-guard at dusk, launching a surprise counterattack against him while Nobuyasu was in the course of withdrawing with only half of his men remaining nearby.
Although married to one of Nobunaga’s younger sisters, Nobukiyo gradually distanced himself from both branches of the Oda clan. Around 1555, he allied himself with the Hachisuka clan. He made an illegitimate attempt to control the villages of Kashiwagi and Shinoki in the Kasugai District of Owari. Dismissing familial ties in his pursuit for more power, Nobukiyo attacked Nobunaga at Gakuden Castle in 1562. Nobunaga’s forces responded by capturing several castles in Nobukiyo’s territory, eventually toppling his base at Inuyama in 1564. Nobukiyo fled to Kai Province to seek protection from the Takeda clan.
Before Nobunaga could achieve his goal to control Owari, he had to eliminate the threat from his younger brother, Nobukatsu. Their mother, Dota Gozen, had raised and cherished Nobukatsu since birth, and his princely character contrasted sharply with Nobunaga’s odd and sometimes brutish countenance. Inevitably, people compared Nobunaga with Nobukatsu, culminating in a personal contest for control of the Oda clan.
In 1555, Nobukatsu disregarded Nobunaga and claimed the title of danjōchū, an official name recognized by the Court traditionally held by the head of the clan. This act marked Nobukatsu as Nobunaga’s primary rival in the family.
In the summer of 1555, Nobunaga’s younger brother, Hidetaka, was accidently slain by Suga Saizō, a retainer of Oda Nobutsugu, lord of Moriyama Castle. This occurred when Hidetaka rode by on his horse near Nobutsugu and some of his retainers who were enjoying a fishing expedition on the Shōnai River. Without confirming his identity, Saizō deemed him rude for failing to dismount from his horse and fatally shot him with an arrow. Nobukatsu became enraged at this news, and responded by burning down some of the area below Moriyama Castle. Nobunaga admonished Nobukatsu and argued that Hidetaka bore responsibility for venturing out in a defenseless posture. Nobukatsu’s defense of family ties in this incident caused retainers in the Oda clan to further desire him as the successor to head of the clan.
In 1556, Nobunaga’s father-in-law and advocate, Saitō Dōsan, was defeated by Yoshitatsu, his eldest son, and perished. Nobukatsu then allied with Hayashi Hidesada, Hayashi Michitomo, and Shibata Katsuie to take up arms against Nobunaga, and attempted to seize the villages of Shinoki in Nobunaga’s territory. In the eighth month, Katsuie lost in the battle at Inō, and Michitomo perished. Katsuie confined himself in Suemori Castle, but through the intervention of Dota Gozen, the mother of Nobunaga and Nobukatsu, Hidesada and Katsuie were pardoned.
In 1557, Katsuie conspired with Nobuyasu, lord of Iwakura Castle, to plan another rebellion and aimed to capture the villages of Shinoki. This time, however, Katsuie notified Nobunaga of the plot. Thereafter, Nobukatsu received news that Nobunaga was ill, and inquired with Katsuie as to the veracity of the rumor. Katsuie said if you deceive Nobunaga by having him sign a formal document acknowledging Nobukatsu as the successor to Nobuhide, then you take control of the Oda clan because Nobutomo is also away. Then, on the second day of the eleventh month, while attempting to visit Nobunaga at his quarters in Kiyosu Castle, Nobukatsu was assassinated under orders from Nobunaga by one of Nobunaga’s retainers named Kawajiri Hidetaka near the north tower to the castle.
For several years after the death of Nobuhide, the two brothers managed to cooperate sufficiently to ward-off opponents to the clan. However, they had a gradual falling out hastened by influential people around them. Several key retainers of the Oda family, headed by Hayashi Hidesada and Shibata Katsuie, devised a conspiracy to support Nobukatsu as the successor of Nobuhide. In short, they had little confidence in the capacity of Nobunaga to lead and protect the family. Hidesada, one of the elders at Nagoya Castle, remained after Nobunaga had moved on to Kiyosu and attempted unsuccessfully to draw Nobunaga into Nagoya Castle. Sakuma Nobumori served as Nobunaga’s closest ally and as a loyal retainer of Nobuhide as well.
The conspiracy led to action in the autumn of 1556, at which time Nobukatsu served as lord of Suemori Castle. Backed by Hidesada and Katsuie, Nobukatsu seized territory under the direct control of Nobunaga and launched a rebellion. Nobunaga’s mounted soldiers first clashed with the enemy near the village of Inō on the outskirts of the city of Nagoya. Katsuie led one thousand men down the nearby road, while Hayashi Michitomo led another seven hundred men across the fields from the south. Outnumbered more than two to one by his powerful opponents, Nobunaga temporarily retreated, but, after regrouping, he prevailed, capturing over four hundred and fifty heads. Nobunaga also killed Hidesada’s younger brother, Michiharu, and prepared to attack Nagoya Castle. Nobukatsu sought refuge in Suemori Castle, and Nobunaga pardoned him in response to desperate pleas from his mother. He also forgave Hidesada and Katsuie. They and other retainers admired Nobunaga’s battlefield tactics, causing them to reconsider their views about him. Nobukatsu showed no gratitude for his release, and remained intent on challenging Nobunaga as the successor to their father.
The next year, Nobukatsu conspired with Nobukata to continue his opposition to Nobunaga. Nobukatsu also sought support from Imagawa Yoshimoto. The plan appeared viable until Nobunaga learned of the conspiracy from Katsuie and devised a response. Nobunaga ordered Katsuie to spread a rumor that Nobunaga was ill. Late in 1557, Nobukatsu placed his trust in Katsuie by paying a visit to Kiyosu Castle to confirm Nobunaga’s condition. As soon as Nobukatsu entered the castle, Nobunaga had him captured and killed.
In early 1559, Nobunaga’s men ransacked the town surrounding Suemori Castle, and then launched flaming arrows into the castle grounds. Next, they set up several rows of fences, and infantrymen encircling the besieged castle launched a barrage of fire. As the fall of the castle and the unification of Owari approached, Nobunaga used the opportunity to slip out of the province in the second month of the operation to pay a visit to the shōgun, Ashikaga Yoshiteru, in Kyōto. Nobunaga announced that he had conquered Owari, and obtained official recognition from Yoshiteru for his position.
By this time, Nobunaga had essentially wiped out his opposition within the Oda clan. Nobunaga, however, began with only a small corner of Owari, and had yet to attain control of the province. Although the influence of the shugo and shugodai had waned, he still faced the threat of the powerful Imagawa, who had steadily expanded their reach into the eastern portions of Owari throughout the period of struggle within the Oda clan. Expelling the Imagawa would be vital for the next stage of conquest in Mino. After finally consolidating control of the Oda clan following the defeat of Nobukatsu, Nobunaga built forts near Narumi Castle, and surrounded Okabe Motonobu.