The siege of Osaka (大坂の役, Ōsaka no Eki; or, more commonly, 大坂の陣 Ōsaka no Jin) was a series of battles undertaken by the Japanese Tokugawa shogunate against the Toyotomi clan, ending in that clan's destruction. Divided into two stages, the winter campaign and the summer campaign, it lasted from 1614 to 1615. The siege put an end to the last major armed opposition to the establishment of the Tokugawa shogunate. The end of the conflict is sometimes called the Genna Armistice (元和偃武, Genna Enbu), because the era name was changed from Keichō to Genna immediately following the siege.
Background
When Toyotomi Hideyoshi died in 1598, Japan came to be governed by the Council of Five Elders, among whom Tokugawa Ieyasu possessed the most authority. After defeating Ishida Mitsunari in the Battle of Sekigahara in 1600, Ieyasu essentially seized control of Japan for himself and abolished the council. In 1603, the Tokugawa shogunate was established with its capital at Edo. Hideyoshi's son Toyotomi Hideyori and his mother Yodo-dono were allowed to stay at Osaka Castle, a fortress that had served as Hideyoshi's residence. Hideyori remained confined to the castle for several years. In addition, as a mechanism of control, it was agreed that in the year 1603 he would marry the daughter of Tokugawa Hidetada, Senhime, who was related to both clans. Ieyasu sought to establish a powerful and stable regime under the rule of his own clan. Only the Toyotomi clan, led by Hideyori under the influence of Yodo-dono, remained an obstacle to that goal.
In 1611, Hideyori finally left Osaka, meeting with Ieyasu for two hours at Nijō Castle. Ieyasu was surprised by Hideyori's behavior, which ran contrary to popular belief that the boy was just "useless". This belief had been spread by Katagiri Katsumoto, Hideyori's personal guardian assigned by Ieyasu since 1599, and who had the intention of dissuading any aggression against the heir. In 1614, the Toyotomi clan rebuilt Osaka Castle. At the same time, the head of the clan sponsored the rebuilding of Hōkō-ji (Great Buddha of Kyoto) in Kyoto. These temple renovations included the casting of a great bronze bell, with inscriptions that read "May the nation be at peace" (国家安康, kokka ankō), and "May the lord and [his] vassals be prosperous and cheerful" (君臣豊楽, kunshin hōraku). The shogunate interpreted "kokka ankō" (国家安康) as shattering Ieyasu's name (家康) to curse him, and also interpreted "kunshin hōraku" (君臣豊楽) to mean "Toyotomi's force (豊臣) will rise again," which meant treachery against the shogunate. Tensions began to grow between the Tokugawa and the Toyotomi clans and only increased when Toyotomi began to gather a force of rōnin and enemies of the shogunate in Osaka. Ieyasu, despite having passed the title of shōgun to his son in 1605, nevertheless maintained significant influence.
After the Hoko-ji Temple Bell Incident, Yodo-dono sent Lady Okurakyo, Lady Aeba and Katagiri Katsumoto to Sunpu to see Tokugawa Ieyasu. In this meeting, Ieyasu hatched a plot to induce a split among the people of the Toyotomi family. On one hand, Ieyasu proposed a generous demand towards Lady Okurakyo. On the other hand, Ieyasu made severe demands on Katagiri Katsumoto, who represented the moderates and had been separately asking Ieyasu to save the Toyotomi family.
Despite Katagiri Katsumoto's attempts to mediate the situation, Ieyasu found the ideal pretext to take a belligerent attitude against Yodo-dono and Hideyori. The situation worsened in September of that year, when the news reached Edo that in Osaka they were grouping a large number of rōnin at the invitation of Hideyori. Katsumoto proposed that Yodo-dono be sent to Edo as a hostage with the desire to avoid hostilities, which she flatly refused. Suspecting him of trying to betray the Toyotomi clan, Yodo-dono banished Katsumoto and several other servants accused of treason from Osaka castle, sending them to the service of the Tokugawa clan. Consequently, any possibility of reaching an agreement with the shogunate was dissolved. This last incident led to the beginning of the siege of Osaka.
Preparations
As preparations, Hideyori sent many letters to most of the daimyo lords in Japan who he predicted would sympathize with the Toyotomi clan. However, his efforts were largely fruitless as his letters delivered by his couriers were rejected by many of the recipients. Hachisuka Iemasa at first was hesitant, until his son convinced him not to accept Hideyori’s invitation to rebel against the Shogunate. Meanwhile, Shimazu Tadatsune directly rejected his invitation as Tadatsune stated the Shimazu clan was still recovering from the Sekigahara war and had no intention to stand up against Ieyasu. Tadatsune also returned a sword gift from Hideyori. An envoy of the Toyotomi clan dispatched to convince Ikeda Tadakatsu, lord of Sumoto in Awaji Island and son of Ikeda Terumasa, also failed, as the Ikeda clan instead arrested the envoys. Furthermore, the Toyotomi clan also failed to convince the Mōri clan under the lead of Mōri Terumoto to join their side, Terumoto instead supported the Tokugawa shogunate, as on November 3, Terumoto ordered his vassals Mōri Motochikazu and Motoyuki Sugimori, who were in charge in Mori Hidemoto's absence, to send half of the troops east if Hidemoto asked them to march out to aid the shogunate in fighting the Toyotomi, while the remaining half, including Sugimori, Motoyoshi Nishi, and Shichirobei Misawa, were to stay in Chofu as caretakers, and to retreat to Hagi if something happened that would make it impossible to maintain Chofu.
Meanwhile, the shogunate also prepared their war efforts by stockpiling their ammunition. In May, a company of British merchants tried to sell lead in Hirado, but failed to find a buyer. This incident was reported by William Adams to the shogunate, who purchased the entire quantity of lead on offer. Furthermore, in the same month a Dutch merchant company was also selling lead, which was also purchased by the shogunate. Later in June, Tokugawa Ieyasu purchased a large amount of cannons, gunpowder, and bullets from British merchants, with Adams acting as the middleman, the prices being 1 kan for cannons, 2.3 bun for gunpowder, and 1.6 bun for bullets.
Winter campaign
In November of 1614, Tokugawa Ieyasu decided not to let this force grow any larger, and led 164,000 men to Osaka. The count does not include the troops of Shimazu Tadatsune, an ally of the Toyotomi cause who nevertheless did not send troops to Osaka. The siege began on 19 November, when Ieyasu led 3,000 men across the Kizu River, destroying the fort there. A week later, he attacked the village of Imafuku with 1,500 men, against a defending force of 600. With the aid of a squad wielding arquebuses (a weapon widely used by Japanese forces at this time), the shogunate forces claimed another victory. Several more small forts and villages were attacked before the siege of Osaka Castle itself began on 4 December.
The Sanada-maru was an earthwork barbican defended by Sanada Yukimura and 7,000 men, on behalf of the Toyotomi. The Shōgun's armies were repeatedly repelled, and Sanada and his men launched a number of attacks against the siege lines, breaking through three times. Ieyasu then resorted to artillery (including 17 imported European cannons and 300 domestic wrought iron cannons) and men digging under the walls.
During this siege, the Tokugawa forces also deployed irregular auxiliaries such as Ninja clans from Iga province under the lead of Ii Naotaka, the head of the Ii clan. Aside from Naotaka's ninja troops, there were also other Iga ikki warriors under Hattori Hanzō, and Yamaoka Kagetsuge. Aside from the ninja forces, other irregular elements from Iga province such as Tōdō Takatora's Musokunin" (part time samurai) also fought in this battle.
Bombing of Osaka Castle
Ieyasu, realizing that the castle would not fall easily and after consulting with his top advisers, ordered a limited bombing which began on January 8, 1615. For three consecutive days, his forces bombarded the fortress at 10 o'clock at night and at dawn. Meanwhile, miners were making tunnels under the walls and arrows were thrown inwards with messages requesting the surrender of the occupants. By January 15, with no response from the besieged, Ieyasu began an incessant bombardment that had a mainly psychological effect to diminish the morale of the defenders. The stone bases of Japanese castles were invulnerable to the artillery of the era and the structure of the castle remained virtually undamaged.
Realizing that the defenses were extremely strong, Ieyasu tried to convince Sanada Yukimura to change sides. Yukimura, who felt a strong antipathy for Ieyasu, rejected the bribe and made the attempt public. Ieyasu then bribed another captain, a commander named Nanjo Tadashige, asking him to open the castle gates. The attempted treason was discovered and Nanjo beheaded, so Ieyasu changed his strategy. Ieyasu ordered his men to deliberately bomb Yodo-dono's quarters, and when they had found the range, a cannon hit its target, killing two of her maids.
During the night of the 16th, Ban Naotsugu, in charge of the defenses of one of the west side doors, carried out a night attack on the troops of Hachisuka Yoshishige, killing several enemies before retreating. The bombing continued the next day, on the mournful anniversary of Toyotomi Hideyoshi's death. Ieyasu thought that on that day Hideyori would be in the temple dedicated to his father, so he ordered that his forces fire towards the place. The projectile almost hit Hideyori's head, hitting one of the pillars of Yodo-dono's quarters. She became terrified and pressed to reach an arrangement with the shogunate.
Peace negotiations
On January 17, Ieyasu sent Honda Masazumi, accompanied by Lady Acha, to meet with Kyōgoku Tadataka, son of Ohatsu, younger sister of Yodo-dono. During the meeting, Lady Acha assured Ohatsu that Ieyasu had no ill will to Hideyori and that he wished to forgive him, but Hidetada was stubborn about taking the castle, so he had thousands of miners working in tunnels under the pits. On the other hand Honda assured that Ieyasu would allow Hideyori to keep Osaka as his fief, but in case he wanted to leave he would give him another one with higher income, besides that all his captains and soldiers would be given free transit when leaving or they could stay inside if they wanted to, but he would need some hostages as a sign of goodwill.
Ohatsu conveyed the terms to Yodo-dono who, in terror, asked Ōno Harunaga, Oda Nobukatsu, and Hideyori's top seven advisers to accept the terms of the surrender. Lady Acha and Honda met again with Ohatsu, Lady Aeba and Ōkurakyō no Tsubone (Yodo-dono's former wet nurse and one of the most influential figures in Osaka castle), and they told him that the outer pit should be filled by Ieyasu's men. On January 21, the Oda delivered their children as hostages and Hideyori sent Kimura to Chausayama to close the agreement. Ieyasu issued a document, sealed with blood from his finger and signed also by Hidetada, which said:
(that) the rōnin in the castle are not found guilty; that Hideyori's income remain the same as before; that Yodo-dono is not asked to live in Edo; that if Hideyori chooses to leave Ōsaka he may choose any other province as his fiefdom; that his person is inviolable.
On January 22, Ieyasu received a solemn oath from Hideyori and Yodo-dono that Hideyori would not rebel against Ieyasu or Hidetada and that he would consult any matter directly with him. Both Honda Tadamasa and Honda Masayuri were entrusted to dismantle the castle's exterior defenses, so the soldiers of the shogunate tore down the walls and filled the outer moat. Hideyori did complain indignantly to the workers that this had not been part of the arrangement, but the response he received was that they only followed Ieyasu's orders. Honda Masazumi blamed the workers for having misunderstood their instructions because they were already filling the interior moat as well. Although the work stopped momentarily, soon the soldiers of the shogunate continued, so Yodo-dono sent one of her bridesmaids and Ōno to Kyoto. Several days later Ieyasu gave an elusive official response, where he assured that since he had signed an eternal peace, the walls were not necessary.