Date Masamune


Date Clan

Mutsu Province

Date Masamune

Lifespan:  8/3 of Eiroku 10 (1567) to 5/24 of Kanei 13 (1636)

Name Changes:  Bontenmaru → Masamune

Other Names:  Tōjirō, Dokuganryū (nickname meaning One-Eyed Dragon)

Rank:  sengoku daimyō

Title:  Junior Fifth Rank (lower) and Master of the Eastern Capital Office, Chamberlain, Governor of Echizen, Junior Fourth Rank (Lower) and Provisional Major General of Imperial Guards of the Right Division, Governor of Mutsu, Senior Fourth Rank (Lower) and Councilor, Junior Third Rank and Provisional Vice-Councilor of State, Junior Second Rank (honorary)

Clan:  Date

Bakufu:  Edo

Domain:  Sendai

Lord:  Toyotomi Hideyoshi → Toyotomi Hideyori → Tokugawa Ieyasu → Tokugawa Hidetada → Tokugawa Iemitsu

Father:  Date Terumune

Mother:  Yoshihime (daughter of Mogami Yoshimori)

Siblings:  Masamune, Kojirō, Hideo, Senshihime

Wife: [Formal] Megohime (daughter of Tamura Kiyoaki), [Consorts] Shinzō-no-kata, Iisaka-no-tsubone, Oyama-no-kata, Shōgonin, Katsumehime, Myōhan

Children:  Hidemune, Tadamune, Munekiyo, Muneyasu, Munetsuna, Munenobu, Munetaka, Takematsumaru, Munezane, Munekatsu, Watari Munemoto, Irohahime, Muuhime, Minehime, Sengikuhime, Tsuda (Geigetsu-in)

Adopted Children:  A

Date Masamune served as a sengoku daimyō of Mutsu and Dewa provinces from the Sengoku to early Edo period.  Masamune served as the seventeenth head of the Date clan and, in the Edo period, as the founder of the Sendai domain in Mutsu.  He was honorarily referred to posthumously as Lord Teizan.  As a young child, Masamune contracted smallpox which left him blind in the right eye.  Given that he could use only one eye, in later eras, he received the nickname of the One-Eyed Dragon.


On 8/3 of Eiroku 10 (1567), Masamune was born as the eldest son of Date Terumune, a sengoku daimyō and the sixteenth head of the Date clan based at Yonezawa Castle in Dewa Province.  His mother was Yoshihime, the formal wife of Terumune and the daughter of Mogami Yoshimori (and younger sister of Mogami Yoshiaki).  Masamune’s childhood name was Bontenmaru.

On 11/15 of Tenshō 5 (1577), Masamune attended his coming-of-age ceremony and was given the name of Date Tōjirō Masamune.  Bontenmaru firmly refused but was compelled to use the name by his father, Terumune.  His true name of Masamune originated from Daizen Daibu Masamune, the ninth head of the clan in the Muromachi period who was revered as the ancestor who rejuvenated the family dynasty, and to distinguish him from this ancestor, he was given the name Tōjirō Masamune.  Until then, the heads of the Date family had customarily received one of the characters from the name of the Ashikaga shōgun, but at the time of Masamune’s coming-of-age ceremony, Ashikaga Yoshiaki (the fifteenth shōgun) had been ousted from the capital by Oda Nobunaga, so the clan was unable to make the request.

In the tenth month of 1579, Tamura Kiyoaki (a sengoku daimyō from Mutsu and lord of Miharu Castle) consulted in regard to the marriage of his daughter to Masamune, including confirmation of the date for a wedding procession, security measures, and other details.  That winter, Masamune (at the age of thirteen) received as his formal wife Megohime (at the age of twelve), the only daughter of Kiyoaki.  Date Tanemune was the great-grandfather of both Masamune and Megohime.  The palanquin was carried from Yanagawa Castle in the Date District.  With Date Shigezane and Endō Motonobu providing security, the procession avoided the Itaya Pass and instead traversed the Kosaka Pass, Shichi-ka-shuku, and the Niijuku Pass, arriving at Yonezawa Castle in Dewa Province.

Early in the fifth month of 1581, Masamune deployed for the first time in a battle against a neighboring sengoku daimyō – the Sōma clan.  From around this time, Masamune served as the representative of Terumune in diplomatic matters with the Tamura and Ashina clans.  Through the efforts of Masamune, Ashina Morioka agreed to send reinforcements to the Date in their battle against the Sōma.

From succession to the clan to the Battle of Suriagehara

In the tenth month of 1584, following the retirement of Terumune, Masamune became the seventeenth head of the Date family.  At this time, Masamune said he would refuse the succession owing to his young age, but, through the counsel of senior members of the family, he assumed the headship of the clan.  The succession occurred over the period from 10/6 to 10/22.  The last known document issued by Terumune as head of the clan is dated 10/5 while the first-known document issued by Masamune is dated 10/23.  This was a response to a query from Ishikawa Akimitsu (Terumune’s younger brother) to news of Terumune’s retirement.

On 10/6, on the same day as the beginning of the transition from Terumune to Masamune, Ashina Moritaka was assassinated by his retainers in Aizu.  Years earlier, Terumune sent a letter to Ashina Moriuji (the adoptive father of Moritaka) to propose that Moriuji adopt Terumune’s second son, Kojirō, after he grows up so that Kojirō would become the eventual head of the Ashina family.  One month before the assassination, however, Moritaka’s wife, Hikohime (Terumune’s younger sister) bore a son named Ashina Kameōmaru.  Satake Yoshishige of Hitachi Province opposed the plan for Kojirō to take over, and after sending a letter to the Ashina family indicating his support for Kameōmaru as the successor, the plan initiated by Terumune backing Kojirō failed.  This served to hasten the retirement of Terumune and was also a factor in Masamune’s breaking of the alliance with the Ashina.  Under an alternative view, soon after inheriting the family, Masamune endeavored to restore the relationship with the Ashina and, as for Terumune, having seen the ensuing chaos in the Ashina family after the unexpected demise of Moritaka, he decided to have Masamune succeed him while Terumune was still healthy to avoid a similar outcome.  This was a more important factor in his retirement than the succession issues in the Ashina clan.

Ōuchi Sadatsuna, the lord of Obama Castle, joined forces with Nihonmatsu Yoshitsugu, the lord of Nihonmatsu Castle, sought to liberate himself from control by the Tamura clan.  The Ōuchi requested support from the Ashina while the Tamura requested support from the Date.  Under these conditions, Ashina Moritaka and Yoshitsugu proposed to Terumune and Masamune a reconciliation between the Tamura and the Ōuchi.  Meanwhile, prior to the succession to Masamune, Terumune was engaged in diplomacy with the Ashina, attempting to mediate a settlement between the Ashina, the Iwaki, and the Tamura.  However, as a son-in-law of the Tamura, Masamune refused and, after the demise of Moritaka, the Ashina would not agree.  A failure to reach a settlement between the Date and Tamura on one side and the Ashina and Ōuchi on the other brought to an end a long-running alliance between the Date and Ashina clans.

In the fifth month of 1585, Masamune attacked Hinohara in the Ashina territory, and, in the eighth month, advanced his forces to Odemori Castle in the Ōuchi territory.  As a warning to those in neighboring provinces, the forces made a clean sweep, slaughtering everyone in the castle.  Ōuchi Sadatsuna abandoned Obama Castle and fled to Nihonmatsu Castle, and then went to Aizu for the protection of the Ashina.  Having seen this outcome, Nihonmatsu Yoshitsugu proposed a settlement, and through the mediation of Terumune, his rights to only five villages in the territory of Nihonmatsu were recognized.  Meanwhile, after Terumune stepped outside his castle to send-off Yoshitsugu who had come to thank him for the recognition of his rights to territory, Terumune was abducted.  This event is known as the Awanosu Incident.  At the time, Masamune was engaged in a falconry outing.  Upon hearing the news, he quickly returned and pursued Yoshitsugu.  In the ensuing clash, Terumune and his abductors were all killed by arquebus fire.  There is a theory that the men who were engaged in falconry were carrying arquebuses as part of a plan for Masamune to kill his father.

On 10/15, after the completion of memorial services, Masamune, in a war of vengeance for his father, joined with Tamura Kiyoaki and Sōma Yoshitane to attack Nihonmatsu Castle defended by Araki Moritsugu.  On 11/2, an allied army was formed for the purpose of reinforcing Nihonmatsu whereupon Masamune left an army behind to continue the siege of the castle and led elite forces south toward Motomiya Castle to counter the allied army.

On 11/17 of Tenshō 13 (1586), the Date army violently clashed near Setogawa in the Battle of Hitotoribashi in the Adachi District with allied forces comprised of 30,000 soldiers from clans in the southern Oushū region led by the Satake who had gathered to support the defense of Nihonmatsu Castle.  Outnumbered, the Date forces scattered in defeat while Masamune himself confronted a dangerous situation amid a hail of arrows and bullets.  Through the efforts of a senior retainer named Oniniwa Yoshinao, who sacrificed himself serving as the rear guard, Masamune was able to retreat and, the following day, owing to the withdrawal of the Satake army, narrowly escaped with his life.

In the third month of 1586, Emperor Ōgimachi offered to award the title of Governor of Mimasaka to Masamune in exchange for donations to support the reconstructions of the main hall of the Enryaku Temple that had been burned down by Oda Nobunaga during the attack by burning of the monastery on Mount Hiei.  However, owing to the difficulty of garnering support amid increased tensions in the surrounding area, in the eighth month of 1586, Masamune formally declined the title of Governor of Mimasaka in a meeting with a messenger from the Shōren monastery in Kyōto.  It is also possible that he declined on the grounds that the title of Governor of Mimasaka was a lower rank than the title of Master of the Eastern Capital Office that had been given to the hereditary heads of the Date clan since Tanemune.  Nevertheless, Imperial edicts and communications did not have an impact on the Shōren monastery that was attempting to mediate the matter.

In the fourth month of 1586, Masamune himself joined a deployment on horseback to lay siege to Nihonmatsu Castle while the Hatakeyama clan supported the head of the clan, Kuniōmaru (later known as Nihonmatsu Yoshitsuna) to vigorously resist.  In the seventh month, through the efforts of Sōma Yoshitane, the Date and Ashina clans settled whereupon Kuniōmaru vacated Nihonmatsu Castle and and went into exile under the protection of the Ashina in Aizu.  By this means, the Nihonmatsu-Hatakeyama clan was in fact eliminated.  Thereafter, Masamune promoted reconciliation with the Satake clan and other daimyō from the southern Oushū, temporarily bringing peace to the region.  In the eleventh month, after Ashina Kamewakamaru suddenly died at the age of three, Satake Yoshishige, backed his own son, Satake Yoshihiro, to become the head of the Ashina clan.  However, Yoshishige obtained prior consent from the Shirokawa-Yūki and Iwaki clans to back Yoshihiro but did not notify Masamune who appeared to back his younger brother, Kojirō.  Masamune viewed this as a desire by the Satake clan to exclude the Date clan so he committed to an all-out showdown with the Satake.

In the twelfth month of 1587, Toyotomi Hideyoshi (the kanpaku, or Chief Advisor to the Emperor) issued an order to the daimyō of the Kantō and Ouu regions, especially toward the Hōjō clan of the Kantō and the Date of the Oushū, which prohibited armed conflict between provincial daimyō over territorial or personal matters.  Masamune, however, disregarded the order and continued fighting.

In the second month of 1588, Masamune intervened in an internal conflict in the Ōsaki clan to the north, attacking with 10,000 soldiers, but, owing to abandonment by Kurokawa Haruuji and stiff resistance by supporters of the Ōsaki, he lost.  Moreover, Masamune’s uncle, Mogami Yoshiaki, became increasingly opposed to Masamune, participating in the battle on behalf of Ōsaki Yoshitaka, his brother-in-law.  In the Battle of Ōsaki, the Mogami forces launched attacks across the Date territory.  Meanwhile, the Ashina and Sōma clans took advantage of the preoccupation by the Date with the Battle of Ōsaki to invade the southern portions of the Date territory, toppling Nawashiroda Castle in one of a series of battles known as the Kōriyama Conflict.  However, on the battlefront to the south, Date Shigezane successfully lured Ōuchi Sadatsuna to his side.  On the northern front, in the fifth month, upon the entreaties of Yoshihime (Masamune’s mother), the Date and Mogami agreed to a ceasefire, offering a respite from the fighting.  In the seventh month, the Mogami and Ashina reached a settlement, enabling Masamune a way out of the precarious situation.  He then succeeded in securing the territory of the Tamura clan (the family of his wife, Megohime) in an event known as the Tamura Retribution.  In the ninth month, Masamune communicated his intent, via Kanayama Muneyoshi, to pledge allegiance to Hideyoshi.  Hideyoshi then requested him to visit Kyōto in the first half of 1589.

On 2/26 of Tenshō 17 (1589), Masamune broke his left leg after falling from a horse and had to recuperate.  During this period, in the fourth month, Iwaki Tsunetaka, acting in concert with Sōma Yoshitane, commenced an invasion of the territory of the Tamura clan.  After recuperating from his injury, in the fifth month, Masamune finally deployed, but after the invading forces learned that Katahira Chikatsuna (the younger brother of Ōuchi Sadatsuna) had left the Ashina to return to the service of Masamune, the forces changed direction and headed toward Aizu.  From the fifth to sixth months, he fought against Ashina Yoshihiro of Aizu, defeating him at the Battle of Suriagehara in the foothills of Mount Bandai.  In the wake of his defeat, Yoshihiro abandoned Kurokawa Castle and fled to the Satake (his original family).  This marked the end of the Ashina as a sengoku daimyō family.  Around this time, several senior retainers from the Satake clan such as Yūki Yoshichika, Ishikawa Akimitsu, and Iwaki Tsunetaka who served as the backbone of the clan with respect to interventions in Oushū in observance of the order from Hideyoshi to quell fighting among daimyō switched their allegiance to the Date.  Others, including the Nikaidō clan, who continued their resistance against Masamune were destroyed.  These actions represented a denial of the obedience pledged to Hideyoshi along with his order prohibiting conflicts across provincial borders.  Hideyoshi then made clear that unless the Date withdrew from Aizu, he would deploy his army to the Ouu region (Mutsu and Dewa provinces).

At this time, Masamune controlled the western and central portions of Mutsu along with the southern portions of Dewa, amassing one of the largest territories in the country.  Others falling under his command included gōzoku, or wealthy landowners, such as the Shirokawa-Yūki in southern Mutsu as well as the Ōsaka and Kasai clans who governed areas to the north of Sendai.

The Conquest of Odawara and period under the Toyotomi administration

In the eleventh month of 1589, owing to the invasion by the Gohōjō clan to the territory of the Sanada, Hideyoshi launched a campaign against the Gohōjō.  Dating back to the era of his father, Terumune, the Date maintained an alliance with the Gohōjō clan.  Masamune was therefore confronted with a difficult decision whether to participate in the campaign or else to fight against the Toyotomi.

In the fifith month of 1590, during the siege by Hideyoshi in an event known as the Conquest of Odawara, Asano Nagamasa (a commander for the Toyotomi) demanded that Masamune join the campaign.  On 5/9, Masamune departed from Aizu, passing through Yonezawa and Oguni, and further through Echigo, Shinano, and Kai provinces controlled by his ally, Uesugi Kagekatsu, before arriving in Odawara.  In view of the number of forces mobilized, he submitted to Hideyoshi.  Despite having seized the territory of Aizu, Hideyoshi recognized the rights of the Date family to territory totaling 720,000 koku (approximately the size of the territory that Masamune inherited).  At this time, Masamune proposed to those who had come to question him regarding his decision to join the campaign such as Maeda Toshiie that he would like to receive instruction from Sen no Rikyū in the tea ceremony, drawing the interest of Hideyoshi and others.  Masamune may have done this aware of the natural interest that Hideyoshi had in cultural affairs.  Soon after Masamune pledged his support to Hideyoshi, Hōjō Ujimasa and Hōjō Ujinao (father and son) surrendered, and Hideyoshi conducted the Oushū Retribution (and, as a prelude, the Utsunomiya Retribution) at Utsunomiya Castle in Shimotsuke Province.  By this time, Hideyoshi had completed the unification of Japan, but, as an outcome of these decisions, Masamune lost the territory of Aizu and incurred a reduction of his fief to thirteen districts in Mutsu and Dewa totaling 720,000 koku.  While in Utsunomiya, he met with Nakamura Tokinaga, a retainer of the main branch of the Shimotsuke-Utsunomiya clan.

In 1591, Masamune joined with Gamō Ujisato to suppress the Kasai-Ōsaki Uprising, but then it was discovered that Masamune himself may have instigated the revolt.  These suspicions were triggered by a letter obtained by Ujisato purportedly written by Masamune to the ikki forces.  Moreover, Hideyoshi also heard rumors that the hostage that Masamune had sent to Kyōto was an imposter of his wife and that Masamune’s battle flags were on display in the castle in which ikki forces were holed-up.  Hideyoshi summoned Masamune to come to Kyōto, whereupon Masamune explained that the letter instigating the uprising was fabricated.  Although Hideyoshi ostensibly accepted the explanation, he appropriated six districts in the Date territory including, among them, the Okitama, Shinobu, and Date districts in exchange for thirteen districts in Kasai and Ōsaki that had been laid to ruin during the uprising.  Masamune was then reassigned and demoted from Yonezawa Castle with a fief of 720,000 koku to Iwatesawa Castle (later known as Iwadeyama Castle) in the Tamatsukuri District with a fief of 580,000 koku.  Around this time, Masamune was given the Hashiba surname by Hideyoshi and, given that the territory around Iwadeyama Castle was formerly held by the Ōsaki, adopted the title of Chamberlain of Hashiba Ōsaki.

In 1593, Masamune supported the Bunroku Campaign on the Korean Peninsula.  During the deployment, Masamune had the Date units dress in very elaborate attire, attracting a lot of attention from onlookers as the army marched to Kyōto.  The contingent ranged from 1,500 to 3,000 soldiers.  When other forces passed by, the residents of Kyōto remained quiet but could not help cheering at the splendorous impression made by the Date forces.  Thereafter, any persons who preferred elaborate attire were figuratively called a Date person.  On the Korean Peninsula, on account of ongoing peace negotiations with the Ming dynasty, Masamune was excused from construction of a castle for the Japanese army on the southern shores of the peninsula so he declined military provisions from Hideyoshi.  Masamune demonstrated willingness to actively support the war effort, but did not actually participate in the campaign.

From 1593, Asano Nagamasa served in the role of the toritsugi for Hideyoshi.  In this capacity, in addition to cementing Hideyoshi’s control over the daimyō, he served as an intermediary for negotiations between daimyō such as Masamune and the Toyotomi administration.  In a letter dated 8/14 of Bunroku 5 (1596), Masamune declared that he could not tolerate Nagamasa’s attitude and broke relations with the Toyotomi.  Unlike other daimyō who quickly submitted to Hideyoshi and were selected to serve as the Council of Five Elders, Masamune allied with the Hōjō clan in opposition to Hideyoshi, and was almost the last daimyō to pledge allegiance so he was not heavily relied upon by the Toyotomi administration.

In 1595, Toyotomi Hidetsugu, the kanpaku, or Chief Advisor to the Emperor, was forced by Hideyoshi to commit seppuku on grounds of plotting a rebellion.  Given the friendly relations that Masamune had with Hidetsugu, this event raised tensions among those around Masamune.  Shortly before the incident, Komahide, the daughter of Mogami Yoshiaki and cousin of Masamune on his mother’s side of the family, had moved to Kyōto to become a consort of Hidetsugu.  Owing to this connection, she was executed along with Hidetsugu’s wife and children.  Hideyoshi also suspected that Masamune was involved in the plot and was close to ordering that he be demoted and reassigned to Iyo Province, but he was ultimately pardoned based in part on direct appeals from two retainers of the Date – Yunome Kagayasu and Nakajima Munetomo.  Nevertheless, a total of nineteen senior retainers in Kyōto were required to jointly sign a pledge to the effect that if Masamune showed an intent to rebel, they would immediately force him to retire and transfer headship of the clan to Heigorō (Toyotomi Hidemune).

After the death of Hideyoshi in 1598, Masamune and Tokugawa Ieyasu (a member of the Council of Five Elders) breached the will of Hideyoshi and, in 1599, arranged for Masamune’s eldest daughter named Iroha-hime to wed Ieyasu’s sixth son named Matsudaira Tadateru.  Beginning with Masamune and Ieyasu, with respect to relations between the relations between daimyō, there is a view that the proprietary of marriage for personal reasons was a clear violation of the laws established by the Toyotomi administration.  The fact that this matter was resolved without punishment revealed that these laws had not sufficiently taken root to enable strict enforcement of the will of the deceased Hideyoshi.  Therefore, the view that Ieyasu’s actions were a violation of the law may lack objectivity with respect to the real status of the laws at this time.

The Battle of Sekigahara and Mogami Campaign

In 1600, Ieyasu joined the army formed to eliminate Uesugi Kagekatsu of Aizu.  On 7/25, the forces recovered Shiroishi Castle from Tosaka Katsuno.  While Ieyasu was away from the Kinai, Ishida Mitsunari (a member of the Five Commissioners) and others under the command of Mōri Terumoto, rebelled against Ieyasu.  At the time, Ieyasu and his army were camping near Oyama in Shimotsuke Province en route to confront the Uesugi in the Conquest of Aizu.  In an event known as the Oyama Deliberation, Ieyasu held a military council with his generals to decide whether to continue on their northward march or to return to the Kinai to suppress the rebellion.  Ieyasu then decided to head west and return with his army.  The following month, Ieyasu sent a letter to Masamune permitting Masamune to recover the six districts totaling 490,000 koku of his former territory that had earlier been seized by Hideyoshi and conveyed to the Uesugi at the time that Masamune was demoted and transferred to Iwatesawa Castle (later known as Iwadeyama Castle).  This letter is known as the Guarantee (from a superior) of 1,000,000 koku.  To obtain permission to attack the Waga, Hienuki and Hei districts held by Nanbu Toshinao, Masamune repeatedly asserted to Ieyasu that the Nanbu clan was colluding with the Western Army.  By providing the guarantee, Ieyasu sought to encourage Masamune to focus on battling against the Uesugi.

The Battle of Sekigahara broke out on 9/15 of Keichō 5 (1600).  In the Battle of Keichō Dewa, an army led by Naoe Kanetsugu (a senior retainer of the Uesugi fighting for the Western Army) invaded the territory of the Mogami clan who were affiliated with the Eastern Army.  Based on his affiliation with the Eastern Army, Masamune received a request from the Mogami to send reinforcements.  He then dispatched 3,000 soldiers led by his uncle, Date Masakage.  On 9/25, Oniniwa Tsunemoto attacked Yuhara Castle in the Katta District in territory controlled by the Uesugi.  As a member of the Eastern Army, Tokugawa Ieyasu was on the prevailing side in the Battle of Sekigahara.  Meanwhile, Naoe Tsunetsugu lost to Mogami Yoshiaki and fled to Yonezawa.  Masamune himself then led forces across the Kunimi Pass and in a southwardly directtion with the aim to recover the Date and Shinobu districts.  On 10/6, the Date forces clashed with soldiers led by Honjō Shigenaga, the lord of Fukushima Castle.  Masamune’s forces defeated the Uesugi army led by Daihōji Yoshikatsu (Shigenaga’s son) who had scouted enemy forces at the Miyashiro-omote field battle, but at the ensuing siege of Fukushima Castle, Masamune’s forces were stymied by a vigorous defense waged by Shigenaga, and failed to topple the castle.  Furthermore, their supply lines were severed by detached units of the Uesugi army, so, on the following day, the besieging forces retreated to Kitame Castle.

Later, until around the spring of the next year, forces deployed on multiple occasions to attack Fukushima Castle but, in the end, could not overcome their initial failure.  Territory comprising a total of 20,000 koku in the Katta District of Mutsu was all that the forces could recover from the six districts formerly controlled by the Date.  In addition, it was learned that Masamune had instigated an uprising by Waga Tadachika in the Nanbu territory by ordering Shiroishi Munenao to lead 4,000 soldiers on an invasion of the Nanbu territory in support of Tadachika.  This event was known as the Iwaski Uprising and, although disregarded in the end, the additional awards sought by Masamune were rejected and his fief reduced to 600,000 koku.  Later, his fief totaled 620,000 koku based on an increase of 20,000 koku in a small area partioned from Ōmi and Hitachi provinces.

The Sendai domain and emissaries to Europe during the Keichō era

After the Battle of Sekigahara, in 1601, Masamune received permission from Tokugawa Ieyasu to move his base to Sendai where he commenced construction of a castle and the town below.  In this location, Masamune founded the Sendai domain under the Tokugawa bakufu.  Despite the earlier reductions, his fief of 620,000 koku was the third largest in Japan after the Maeda clan of Kaga and the Shimazu clan of Satsuma.  After receiving the Tokugawa surname from the bakufu, he adopted the title of Matsudaira Mutsu-no-kami.

Sendai Castle was constructed on a mountain, taking advantage of the natural terrain for its defenses.  The comprehensive development of the municipality of Sendai below the castle was a major undertaking that required the mobilization of a total of 1,000,000 people.  To govern the domain, Masamune established residences in forty-eight locations in which he positioned retainers.

Masamune made plans for commerce (Pacific trade) between the Sendai domain and Kingdom of Spain.  In 1613, acting through the help of an emissary of Felipe III of the Kingdom of Spain, Masamune had constructed a Galleon ship named the San Juan Bautista or the Date Maru.  Upon consent of Ieyasu, Masamune appointed Luis Sotelo as his diplomatic emissary and dispatched a retainer named Hasekura Tsunenaga and a crew of over 180 men to New Spain (Mexico), Spain, and Rome, on sea-faring expeditions known as the Keichō Emissaries to the West.  From 1603, Masamune had more contact with retainers of the Tokugawa bakufu.  His connection with these retainers was, in part, to gather information, and, in addition to the exchange of gifts, he enjoyed banquets, music events, tea ceremonies, and performance arts.

In 1613, in a letter sent to his wife, Megohime, while Masamune was in Echigo Province for the construction of Takada Castle, he elegantly described his sense of the spring and autumn seasons and the beauties of nature on the basis of the Buddhist perception of the evanescence of life.​  Distant from his pregant wife, this revealed his sensitive feelings during this time.

The Siege of Ōsaka

In 1614, during the Winter Campaign of the Siege of Ōsaka, Masamune established a base as the army for actions in the direction of Yamato.  After the brokering of a settlement, the Date forces were responsible for the work to fill-in the exeterior moats.  In the twelfth month of that year, Tokugawa Hidetada (the shōgun) awarded to Masamune the territory of the Uwa District in Iyo Province.  In 1615, at the Summer Campaign of the Siege of Ōsaka, Masamune fought against Gotō Mototsugu at the Battle of Dōmyōji.  After suffering wounds in an attack by Katakura Shigenaga (a member of the Date family), Mototsugu then took his own life.  The army for actions in the direction of Yamato decimated the Gotō division that had set-up an encampment in Komatsuyama – a strategic location on the approach to the Dōmyōji.  The soldiers advanced to the village of Honda,  but then the Date forces incurred a counterattack by Sanada Nobushige (Yukimura) and were forced to retreat.  Mizuno Katsunari, the commander of the vanguard units, repeatedly requested Masamune to launch another attack against the Sanada forces, but, among other reasons, owing to a shortage of gunpowder and injuries to troops, Masamune flatly refused and, in the end, Masamune himself went to Katsunari’s position to refuse the requests.  As a result, Nobushige easily recaptured Ōsaka Castle and noted scornfully that even if there were one million warriors from Kantō, there would not be one man among them.  During the battles in the village of Honda, Masamune’s forces killed three members of the Mizuno family (who were allies), and stole horses from the Mizuno, but Katsunari set-up an ambush for the Date, slayed soldiers, and took back the horses.  Masamune did not raise an objection to this outcome.

According to one theory, on 5/7, at the Battle of Tennōji-Okayama, Masamune marched to the entrance to Senba while a battalion led by Jinbō Sukeshige under Mizuno Katsunari clashed with a battalion under Akashi Takenori, killing approximately 300 allied soldiers.  There is also a theory that this occurred over six days in the Battle of Dōmyōji.  The Jinbō battalion was decimated and Sukeshige killed in action while surviving retainers continued to oppose Masamune under the command of Mizuno Katsunari.  On taking the offensive, Masamune noted that the Jinbō battalion had collapsed under attack by the Akashi forces, so steps were taken to prevent his army from being swept into the conflict, and the Date military tactics did not differentiate between enemies and alllies.

Soon after, these rumors gave rise to an abundance of curiosity and speculation.  Under one theory, arquebusiers from the Gotō battalion peremptorily rained fire on the Jinbō battalion while the latter were taking a break from the fighting.  Another theory is the attack was prompted by envy of recognition for their meritorious deeds.  However, there are no records that Masamune was admonished for this incident while records of the Tokugawa bakufu simply note that Jinbō Sukeshige fought valiantly and died.  The bakufu may have shown deference toward Masamune by squelching objections, or it is conceivable that embellished rumors spread of the killing of allies in the Mizuno family.

At the conferral of honors after the war, Date Hidemune (the eldest illegitimate son of Masamune) was awarded a fief of 100,000 koku in Iyo Province which became the Uwajima domain.  Meanwhile, former enemies in battle including Sanada Morinobu (the second son of Sanada Nobushige), along with Akohime (the sister of Chōsokabe Morichika) and her son, Shibata Tomomoto, served the Date family.

The latter years

After circumstances calmed down, Masamune primarily focused his efforts on the development of his territory.  Later, he constructed a waterway called the Teizanbori and developed the Kitakami River Basin for the cultivation of a grain-producing region.  As a result, the Sendai domain with an expected production of 620,000 koku yielded the equivalent of 745,000 koku.  In the field of arts and society, he actively promoted the introduction of culture from the Kyōto area, soliciting technicians and carpenters, giving birth to styles that added peculiar characteristics of the northern provinces to the distinctive splendor of the Momoyama culture.  This produced national treasures such as the Ōsaki-Hachiman Shrine and the Zuigan Temple, along with the Shiwahiko Shrine and the Yakushi Hall at the Mutsu Kokubun Temple.  Masamune brought in Kawamura Magohebei, a land developer residing in Ōmi Province, to build the Ishinomaki Harbor at the mouth of the Kitakami River.  This provided a means to transport rice by boat via the Kitakami River Basin from Ishinomaki and then by sea route to Edo.  Beginning in 1632, rice from Sendai was exported to Edo and, at the peak, one-third of the rice in Edo was said to be Oushū rice.

Masamune served both Tokugawa Hidetada (the second shōgun of the Edo bakufu) and Tokugawa Iemitsu (the third shōgun).  In 1635, Iemitsu promulgated the sankin kōtai system requiring over 250 daimyō nationwide to serve the bakufu in Edo on an alternating basis, leaving their formal wives and heirs in Edo on a permanent basis even while in their own territories.  This system was established to centralize the control and authority of the Edo bakufu over the provinces, preventing local lords from undermining their power.  After Iemitsu announced that the daimyō would henceforth be treated as retainers, Masamune quickly offered to subdue anyone who violated this order, so no one could oppose it.  Iemitsu gave Masamune ten arquebuses for personal protection while outside of his castle.  During the governance of Iemitsu, many of the bushō and daimyō who controlled the battlefields in prior eras had perished; and even though Masamune was reaching an advanced age, Iemitsu respected his unflinching support for the Edo administration, referring to Masamune as the Senior Lord of the Date.  On occasion, upon the urging of Iemitsu, Masamune shared stories with him in regard to Hideyoshi, Ieyasu, and the battles of the Sengoku period.

Masamune looked after his health, but, around 1634, he began to suffer from a loss of appetite and dysphagia.  On 4/18 of Kanei 13 (1636), after a celebration for the completion of the Hoshun Temple in honor of his mother, Yoshihime, Masamune walked down from the castle and, with a staff in hand, pointed to a spot on Mount Kyōgamine, teling those with him to bury him there after he died.  That location later became the site of the Zuihōden, a masoleum in honor of Masamune.  Two days later, on 4/20, after Masamune departed for his assignment in Edo, his symptoms suddenly worsened, and, whole staying in Kōriyama, he could no longer eat.  On 4/28, after arriving in Edo, in addition to having no food, he experienced swelling.  On 5/21, Iemitsu went to the Date residence in Edo to pay a visit to Masamune after coming to Edo despite his deteriorating health.  Masamune washed and properly dressed to welcome Iemitsu.  However, after the visit, when heading back into the home, he rested on his staff, but could no longer move forward.

Early in the morning on 5/24, Masamune died of a combination of esophageal cancer​ and peritonitis​ at the age of sixty-eight.  As expected of a man of the Date, he wished for his wife and children not to see his face upon his death.  On 5/26, the bakufu permitted his territory to be inherited by his eldest son, Date Tadamune.  After preparation of his body, on 6/3, he was returned to Sendai in the same daimyō procession as while he was living.  A total of fifteen retainers and five sub-retainers martyred themselves on his behalf.  Masamune had earlier noted his view that the loss of one eye, even though due to illness, was undutiful to one’s parents.  Therefore, in wooden statues and pictures of him created after his demise, the right eye was shown as a bit smaller or both eyes were shown.  The family of the shōgun issued orders for seven days of grieving in Edo and three days in Kyōto.  This was an exception outside of the three branch families (the Owari, Kii, and Mito) of the Tokugawa.