Although Tokugawa Ieyasu won the battle and Sekigahara and his son became the Shogun, Ieyasu continued to feel uneasy as long as Toyotomi Hideyori continued to be alive and well in the impregnable Osaka Castle.
Ieyasu knew many of his enemies are scattered in Japan and continued to be scheming to destroy him and the Tokugawa Shogunate. A few unsuccessful assassination attempts were made on his life.
As long as Hideyori was still a minor, Tokugawa Ieyasu felt he had nothing to fear. A former Toyotomi supporter, Katagiri Katsumoto tried to convince Tokugawa Ieyasu that Hideyori grew to be an effeminated youth. In the year 1611, Ieyasu met the 18-year old Toyotomi Hideyori during a ceremony and it was said that from then on, Tokugawa Ieyasu decided that he had to destroy Toyotomi Hideyori for once and for all even though Hideyori did not seemed to have any ambition to seize power from Ieyasu.
In the autumn of year 1614, Tokugawa Ieyasu began to move his large army numbering about 200,000 men against Osaka Castle. Sanada Yukimura, an arch-rival of Ieyasu escaped from the monastery he was residing by stealing a horse. This swashbuckling warrior would be Ieyasu’s greatest enemy during the showdown in Osaka Castle. He recruited a large force that was made up of ronins, wanderers, actors, brigands, outlawed Christians and any other people who had a grudge against the Tokugawa Shogunate.
Ieyasu had banned Christianity and persecuted Christians. This drove many of them to turn against the Shogunate. Soon, over 100,000 men were within the walls of Osaka Castle, vowing to destroy Tokugawa Ieyasu and his Shogunate. Among the famous warriors who joined the Osaka defenders included Goto Mototsugu, Kimura Shigenari, Susukida Hayato, Oda Nagayasu, Ujiie Yukihiro, Yamamoto Kimio, Akashi Morishige, Hanawa Naoyuki, Okabe Noritsune, Ban Naoyuki, Akashi Morishige, Ono Harunaga, Ono Harufusa, Chosokabe Morichika and his three sons,
The first battles of the Osaka Winter Campaign began in earnest in the end of November 1614 when Tokugawa’s warriors, known as the Eastern Army fought and reduced several outposts outside Osaka Castle manned by warriors from the Western Army. Both sides suffered significant casualties but Tokugawa Ieyasu was victorious. However, when the Eastern Army under the command of Ii Naotaka and Todo Takatora tried to storm Osaka Castle, they were repulsed by gunfire with heavy casualties.
The Western Army manning Osaka Castle was under the command of Sanada Yukimura, who would be a thorn in the flesh for Ieyasu till the end of the campaign. Tokugawa Ieyasu lost a few thousand men as they were mauled by gunfire from the Western Army.
Tokugawa Ieyasu was frustrated at his failure. Osaka Castle was made impregnable mainly by 2 moats surrounding the castle’s perimeter. Under the competent leadership of Sanada Yukimura, storming the castle would be impossible, if not suicidal. Ieyasu knew if the Western Army could hold back his forces for some time, his hold on power would be precarious. This is because the loyalty of many of the daimyo who did not join forces with the Osaka Castle was questionable and some of them could rise up in support of the defenders if they felt the House of Tokugawa could fall. Tokugawa’s son and successor, Hidetada argued that their men should storm the castle with greater ferocity. Ieyasu disagreed and tried to find a way to bring down Osaka Castle.
In January 1615, Tokugawa Ieyasu ordered his men to fire at the quarters of the mother of at Osaka Castle, the mother of Toyotomi Hideyori in what would be equated as psychological warfare in modern terms. Yodogimi was said to be stunned at the death of two of her maidservants and persuaded Hideyori to try to find a peaceful solution with Tokugawa Ieyasu. Sanada Yukimura and most of other Western Army generals persuaded Hideyori to continue resisting.
They believed if they could hold the castle for one or two years, many of the other daimyos and warriors with dubious loyalty to Tokugawa would rise up and rebelled against Ieyasu. They also believed that Tokugawa Ieyasu cannot be trusted. Unfortunately, Hideyori was naïve to trust Ieyasu and agreed to negotiate peace.
According to the peace deal, Tokugawa Ieyasu would withdraw his Eastern Army from Osaka Castle. On the Western Army part, they would have to allow Ieyasu’s men to fill up the outer castle moat while leaving the inner moat untouched.
Toyotomi Hideyori also had to promise never to try to rebel again. Hideyori agreed to the deals and men from the Eastern Army were allowed to fill up the outer moat of the mighty Osaka Castle. However, after the outer moat had been filled up, Ieyasu’s men proceeded to fill up the inner moat as well. With this, the factor that made Osaka Castle magnificently impregnable was gone.
Ieyasu had obviously instructed his men to fill up both moats. By the time Hideyori and the Western Army knew they have been tricked, it was already too late. If the Eastern Army were to attack Osaka Castle again, the once mighty castle would surely fall.
Hideyori protested against the filling of the inner moat of Osaka Castle. Ieyasu pretended to be surprised. However, Ieyasu said that the inner moat was no longer necessary as he already made peace with Hideyori. Hideyori felt he had been tricked and decided to excavate the inner moat again. He also began to gather more men inside Osaka Castle. When Ieyasu heard that the moat is being dug, he claimed that Hideyori had broken the truce and ordered his men to launch an offensive against Osaka Castle to bring it down for once and for all.
The Osaka Summer Campaign had begun. This time, the Western Army would go on the offensive to intercept the Eastern Army and prevent them from reaching Osaka Castle. And Ieyasu knew that previously his enemies who had been scattered across Japan were now in one place: Osaka Castle.
Osaka Summer Campaign began in the end of April 1615 when Western Army warriors attacked Ieyasu’s approaching Eastern Army near Osaka. However, they were unable to stop the Eastern Army. General Goto Mototsugu’s and his outnumbered men fought valiantly against the Eastern Army in Domyoji. Goto desperately held off Date Masamune’s Eastern Amy while waiting for Sanada Yukimura’s reinforcement to strike the Eastern Army from the rear. Unfortunately, Sanada’s men lost their way in the heavy fog. In the ensuing battle, Goto Mototsugu, his son, Ujifusa and most of the 2,600 Western Army warriors were killed.
Another leading Western Army commander, Kimura Shigenari battled bravely the Eastern Army at Wakae. This young general, who was only in his early twenties was defeated by Ii Naotaka’s Eastern Army. He was beheaded and his head was presented to Ieyasu for viewing in his camp. The youthful general had burnt incense in his helmet and the fragrant odor could be smelled by everyone in the camp. Shigenari had obviously gone to battle knowing that his forces would be defeated and he would be killed.
Mori Katsunaga and Sanada Yukimura placed their arquebusiers against the approaching Eastern Army under Asano Nagaakira. However, their men were staffed by many courageous but impulsive ronins. The firing was disorganized and their element of surprise was compromised. These two commanders desperately tried to stop the haphazard firing by their men but they were too late. Asano’s men got nervous and some Eastern Army commanders thought Asano had turned traitor. However, Asano’s men regained order and they proceeded with the attack on the Western Army.
In the beginning of June 1615, Sanada Yukimura ordered General Akashi Morishige and his 18,500 mostly Christian warriors to strike at the Eastern Army at the rear while he battled them in a place called Tennoji near Osaka Castle. They battled for hours but General Akashi’s warriors never made it to Tennoji. If they had struck Ieyasu’s men, the Eastern Army’s cause would have been lost. General Akashi’s men were intercepted and defeated by Ieyasu’s men before they could reinforce their comrades at Tennoji.
The Western Army at Tennoji fought valiantly but they were soon overwhelmed and Yukimura was exhausted. While he was resting during the battle, an Eastern Army samurai called Nishio Nizaemon challenged Yukimura for a duel. The tired Western Army commander was said to have stated, “I am Sanada Yukimura and a warrior of greater stature than you. But I am now tired and I need rest.” Nishio Nizaemon decapitated the legendary Yukimura’s head.
When their leader was killed, the remnants of the Western Army warriors fled into Osaka Castle and the surrounding woods. The Eastern Army just pursued their fleeing foes all the way to Osaka Castle. It was only at that time that Hideyori decided to march his men out of the castle to face their foes. He was met by thousands of Western Army samurai who were fleeing the onslaught of the advancing Eastern Army.
Soon, the Eastern Army forces aimed their cannons at Osaka Castle and fired. Soon, parts of Osaka Castle were burning. The Eastern Army warriors stormed the castle. Hideyori now knew all was lost. He and his mother, Yodogimi committed seppuku in a section of Osaka Castle. Many of their warriors and servants also committed suicide with their lord while the Osaka Castle was burning. Most of the Western Army warriors were executed by Ieyasu’s men without mercy. Hideyori’s young son, Kunimatsu was tied up and brought before Ieyasu in his camp. The young boy was said to have berated the old samurai before he was decapitated.
Ono Harunaga, Chosokabe Morichika and his three sons were captured days after the fall of Osaka Castle and executed. The heads of thousands of slain or executed supporters of Hideyori were taken and put on rows of racks from Osaka to Fushimi. Few of the Western Army commanders survived the battle and the ensuing dragnet. Akashi Morishige was one of the notable exceptions. In retrospect, many Western Army warriors such as Sanada Yukimura, Kimura Shigenari, Goto Mototsugu and Susukida Hayato fought bravely and exhibited the kind of courage, fighting skills and determination greater than their Eastern Army foes. Ieyasu’s victory and their defeat were just due to fate and destiny.
Tokugawa Ieyasu was now the complete master of Japan. The last resistant to the rule of Tokugawa Shogunate was eliminated. Tokugawa Ieyasu died of illness in June 1616, just one year after the elimination of the Toyotomi threat. He was 73 years old. He left behind a solid shogunate which would rule Japan until the Meiji Restoration in the 1868. This period preceded by that year would be marked largely by long period of peace, isolation and the closing of Japan to the outside world, the brutal persecution of Christianity and extermination of Christians in the country.