Ōkubo Tadachika served as a bushō and hereditary daimyō from the Sengoku to early Edo periods.  Tadachika was the first lord of the Sagami-Odawara domain.

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In 1553, Tadachika was born as the eldest son of Ōkubo Tadayo, a senior retainer of the Matsudaira clan, in Kamiwada in the Nukata District of Mikawa Province.

Beginning in 1563, Tadachika served Tokugawa Ieyasu.  In 1568, he had his first experience in battle during an assault against Horikawa Castle in Tōtōmi Province.  He captured the head of an enemy commander.  Thereafter, as a retainer of Ieyasu, he served in the Mikawa Ikkō-ikki from 1563 to 1564, the Battle of Anegawa in 1570, the Battle of Mikatagahara in 1572, the Battle of Komaki-Nagakute in 1584, and the Conquest of Odawara in 1590.  At the Battle of Mikatagahara, after the Tokugawa army fell into disarray, Tadachika remained at the side of Ieyasu and accompanied him to Hamamatsu Castle.  Later, Ieyasu praised Tadachika for his loyalty and he ranked at the level of a magistrate.

On 6/2 of Tenshō 10 (1582), Oda Nobunaga died in a coup d’ètat known as the Honnō Temple Incident.  At this time, Ieyasu was staying in Sakai, but after receiving news of the coup, he became unsettled, initially going to Kyōto which was temporarily controlled by the Akechi army.  Next, he proceeded to the Chion Temple which had ties to the Matsudaira clan and asserted that he would martyr himself in the wake of Nobunaga’s demise but was convinced by Honda Tadakatsu and others not to take his own life.

Ieyasu then went to his home province of Mikawa.  Tadachika accompanied him in an event known as the Traverse of Iga.  Thereafter, Tadachika supported Ieyasu in the governance of excised territories during the pacification of Kai and Shinano provinces.  At this time, Nagayasu (the natural son of Ōkura Nobuyasu) was selected to demonstrate his skills under Tadachika and he received the Ōkubo surname from Tadachika.

In 1586, during a visit by Ieyasu to the capital, Tadachika was invested with the titles of Junior Fifth Rank (Lower) and Assistant Vice-Minister of Civil Affairs.  He was also conferred the Toyotomi surname.  When Ieyasu entered the Kantō, Tadachika was granted a fief of 20,000 koku in Hanyū in Musashi Province.  In 1593, Tadachika became a chief retainer of Ieyasu’s lineal heir, Tokugawa Hidetada.  In 1594, following the death of Tadachika’s father, Ōkubo Tadayo, Tadachika inherited the headship of the clan in addition to the landholdings, becoming the landlord of 65,000 koku in Odawara in Sagami Province.  Later, he became the first lord of the Sagami-Odawara domain.

In 1600, during the Battle of Sekigahara, Tadachika followed Hidetada who led the main division of the Eastern Army, traveling the Nakasendō linking Nihonbashi in Edo and Sanjō-Ōhashi in Kyōto.  En route, the Tokugawa army attacked Sanada Masayuki (of the Western Army) who was holed-up at Ueda Castle in Shinano Province.  Owing to valiant fighting by the defenders as well as flooding, Honda Masanobu and others sought to lift the siege but Tadachika opposed them and Hidetada decided to continue the assault.  This is known as the Second Battle of Ueda which delayed the arrival of the division to the main battle in Sekigahara.

In 1601, Tadachika was offered to serve as the lord of the Kōzuke-Takasaki domain with a larger fief of 130,000 koku but firmly rejected the proposal.  In 1610, he was appointed to serve as a rōjū, or member of the shōgun’s council of elders, and became an influential figure in the administration of Tokugawa Hidetada, the second shōgun of the Edo bakufu.

Removal from position

On 10/10 of Keichō 16 (1611), Tadachika’s lineal heir, Ōkubo Tadatsune, died from illness, casting a shadow over the continuity of Tadachika’s authority.  On this occasion, persons who went to Odawara without permission from the bakufu to make a condolence call were punished with confinement.  Grieving at the death of his eldest son, Tadachika neglected his political duties, incurring the disfavor of Ieyasu.  After the death of Tadatsune, Hidetada attempted to hold a banquet for Tadachika in the wake of the memorial services but Tadachika refused, disappointing other members of the council of elders.

On 1/8 of Keichō 18 (1613), Yamaguchi Shigemasa was removed from his position for having his son, Yamaguchi Shigenobu, wed the adopted daughter of Tadachika without the permission of the bakufu.  Tadachika’s explanation was that his adopted daughter’s grandfather, Ishikawa Ienari, had earlier obtained permission for the marriage so he concluded it was not necessary for him to obtain permission again and therefore did not seek approval from Hidetada.  Upon receiving the decision of the bakufu, on 1/15, Tadachika became very upset and, on the next day, went with his son to Edo Castle for service.  After the death of a yoriki, or security officer, named Ōkubo Nagayasu, in the fourth month, it was discovered that he had improper accumulations of wealth.  As a result, Nagayasu’s son was compelled to commit seppuku.  This event is known as the Ōkubo Nagayasu Incident.

Amidst these circumstances, in the twelfth month, Ieyasu began a trip to return from Edo to Sunpu.   On 12/6, he arrived in Nakahara in Sagami Province, but after staying for several days, on 12/13, he suddenly returned to Edo.  According to one account of Sunpu, this was to engage in a falconry expedition in Tōgane in the new year.  According to another account, on the preceding day, Doi Toshikatsu came as a messenger of Hidetada to inform Ieyasu that Baba Hachizaemon, a rōnin, or wandering samurai, from the former Anayama clan claimed that Tadachika was plotting a rebellion against the bakufu.  A series of visits by messengers dispatched by Hidetada caused him to return to Edo.  In one account, on 12/7, Itakura Shigemune came as a messenger.

After receiving orders from the bakufu to expel Christians, on 12/19, Tadachika went to Kyōto, and from 1/18 of Keichō 19 (1614), destroyed churches run by Jesuit missionaries from Portugal, compelled Christians to change their beliefs, and banished those who refused.  Nevertheless, on the next day, he was suddenly removed from his position.  He was cast out of his base at Odawara Castle which was destroyed and, on 2/2, Sanmaibashi Castle, the base of Ōkubo Tadasuke whose lineage ended without an heir, was also destroyed.  Thereafter, Tadachika was exiled to Ōmi Province and turned over to the custody of Ii Naotaka.  At this time, he was granted a fief of 5,000 koku in the Nakamura township of the Kurita District.  On 3/1, Tadachika, via a priest named Tenkai, submitted a written explanation to Ieyasu but did not receive a response.  On 3/15, Hori Toshishige was removed from his position for complicity in the events.

Thereafter, he entered the priesthood, adopting the name of Keihan Dōhaku.  On 6/27 of Kanei 5 (1628), he died at the age of seventy-five.  He did not, in the end, receive a pardon from the shōgun family.

Reasons cited for his removal include the unauthorized marriage noted above as well as the complaint from Baba Hachizaemon but this was deemed a complete falsehood from an unworthy individual.  In one account, on 2/1, Doi Toshikatsu met with Ieyasu and informed him that Hidetada was upset because Tadachika had many friends.  The written pledge demanded by the bakkaku (the highest organ in the Edo bakufu) on 2/14 contains a provision prohibiting communications between Tadachika and his sons.  The pledge further stipulates that Tadachika will obey Ieyasu and Hidetada, prohibits bias in adjudications, and states that, in political affairs, the parties would mutually demonstrate their real intentions.  Finally, that communications from Ieyasu and Hidetada would not to be disclosed to others without their permission.

Accounts from the Edo period noted that Honda Masanobu and Honda Masazumi (father and son), who were political opponents of Tadachika, plotted his downfall.  Owing to the involvement of one of Masazumi’s senior retainers in a bribery scandal known as the Okamoto Daihachi Incident, Masazumi was on politically unstable ground and sought to regain his standing by expelling Tadachika.  Primary sources from the time of these events, however, do not make reference to this theory.  A letter from Hosokawa Tadaoki assessed that, after the removal of Tadachika from his position, Masanobu achieved ten times more authority than before his removal.  Following the banishment of Tadachika, Masanobu sent a letter noting that Tadachika’s mother and wife were safe in Odawara – a reference to the persons with whom Tadachika maintained friendly relations that earlier caused the bakufu to request a written pledge from Tadachika.  Meanwhile, Ōkubo Tadataka concluded that Masanobu was indebted to Tadachika so the existence of a dispute between them was a fabrication.

Given the desire of Ieyasu to sweep away vestiges of the Toyotomi administration, there is a theory that he distanced himself from Tadachika who had friendly relations with daimyō from western provinces and promoted peace with them.

Owing to the military contributions of Tadachika over a long period of time, the bakufu permitted his lineal grandson, Ōkubo Tadamoto, to inherit the headship of the clan.  Tadamoto adopted his younger cousin, Ōkubo Tadatomo, who later became the lord of the Odawara domain.  Meanwhile, Tadachika’s second son, Ishikawa Tadafusa, who had been under confinement on grounds of complicity, was pardoned and, based on his contributions during the Siege of Ōsaka, finally became the lord of the Ōmi-Zeze domain while his offspring became the lords of the Ise-Kameyama domain.

Character and anecdotes

Tadachika was informed of his removal on 1/19 of Keichō 19 (1614).  At this time, he was engaged in a game of shōgi at the residence of Tōdō Takatora in Kyōto.  When Itakura Katsushige, the Kyōto shoshidai, or the head of security in Kyōto for the Edo bakufu, appeared without notice as an envoy for Ieyasu, Tadachika understood the situation and said: “After becoming a wanderer, I have not even been able to enjoy shōgi.  Please wait until I finish this game.”  Katsushige acknowledged the request.  The removal of Tadachika triggered fear and turmoil among the residents of Kyōto and its environs.

Following the death of Ieyasu, Ii Naotaka aimed to appeal to Hidetada in regard to the miscarriage of justice against Tadachika, but Tadachika felt this would be disloyal toward Ieyasu so rejected the plan.

There is a story that, after the Battle of Sekigahara, Ieyasu gathered together his senior retainers to discuss a successor.  After some of those in attendance raised the names of Hidetada’s older brother, Yūki Hideyasu, and his younger brother, Matsudaira Tadayoshi, Tadachika recommended Hidetada.

During an event known as the Hidetsugu Incident, Toyotomi Hidetsugu plotted to take Hidetada hostage and then have Ieyasu mediate for him.  Tadachika, however, deftly turned away messengers sent by Hidetsugu twice and, during this time, had Hidetada take refuge in a residence in Fushimi to avoid danger.

Tadachika enjoyed the tea ceremony and learned from Furuta Oribe (Furuta Shigenari, a daimyō and tea master).  He maintained a tea ceremony arbor and garden at which he hosted daimyō from the Kyōto area.  He also offered tea to messengers and gave them horses.  For this reason, he purchased many horses from Ōshū and kept them in Edo and Odawara.  Honda Masanobu voiced his differences with these acts and advised that he request a transfer from Odawara, but Tadachika responded that it is expected that he be granted Odawara which pronouncement became an issue.