After the victory at Sekigahara, and being proclaimed Shogun in 1603, Tokugawa Ieyasu turned his attention towards stabilizing Japan's governmental system. It was essential that he maintain dominance and control over his rival Daimyo. To remedy the situation, Ieyasu instituted a new system, baku-han,which would be a conglomerate of two essential entities; the shogunate and the domains of the individual lords. This system was backed up by his army, wealth, and his personality; but, this still did not keep others from challenging his authority. In 1614, Hideyori, son of Hideyoshi, would challenge the Tokugawa regime.

The new conflict started when Hideyori completed the construction of the 'great Buddha,' which had been destroyed by an earthquake in 1596. Near completion, Hideyori also had a bell made to accompany the idol. On this bell was inscribed "may the state be peaceful and prosperous," which contained the ideographs 'Ie' and 'yasu.' Also inscribed was "In the east it greets the pale moon, and in the West bids farewell to the setting sun." Ieyasu took offense at both of these as alluring to him, the latter as comparing him to Hideyori. Tensions rose on both sides.

Hideyori began appealing to the Daimyo for assistance, many who had once served Hideyoshi, or who were defeated at Sekigahara, lent their aid. Among these were Sanada Yukimura, Ono Harunaga and Harafusa, Kimura Shigenari, Chosokabe Morishige, Goto Mototsugu, and Oda Yuraku--brother of Nobunaga. Soon ronin from all over were flocking to Hideyori's banner, particularly a large number of Christians (Ieyasu had earlier begun a program of ridding Japan of the Christians and executed many). In all, some 90,000 men packed into the fortress of Osaka. Ieyasu assembled his army, some 195,000 strong, and marched to lay siege to Osaka.

The Winter campaign began with a series of attacks against the Osaka defenses. On November 19 Hachisuka Yoshishige and 3,000 men attacked a fort held by 800 men under Akashi Morishige, and succeeded in capturing it. On the 26^th an engagement at Imafuku took place. Here 1,500 Easterners under Satake Yoshinobu took on 600 Westerners under Yado and Iida. The western troops were driven back, and Kimura Shigenari and Goto Mototsugu raced out of Osaka to take on the pursuing Satake; driving them back and nearly destroying them. In the end, a reinforcement from Uesugi Kagekatsu arrived and turned defeat into victory for the East. Earlier that same day, Uesugi and 5,000 troops fought a battle near the Shigeno river against 2,000 Westerners. Reinforcements, which included a big contingent of arquebusiers under Niwa Nagahide and Horio Tadaoki, arrived and drove back the Westerners. On the 29^th two naval operations took place. The first was by Ishikawa Tadafusa against a fort that controlled the approaches to the Kizu river. Aided by Hachisuka Yoshishige, who attacked the fort from the east and south, Ishikawa launched his 2,300 from the west and captured the fort. At the same time a second naval action was fought by Kuki Moritaka with 1,600 against Ono Harunaga's 800 men. The goal was to prevent any western reinforcements from being sent to relieve the fortress guarding the Kizu; the goal was achieved. Having moved their positions closer to the walls of Osaka, Ieyasu ordered his Daimyos to attack the only barrier that still remained outside the outer moat; this barrier was called the 'Sanada barbican.' In the 'U' shaped stockade stood 7,000 heavily armed men under Sanada Yukimura. On December 4 Ii Naotaka, Matsudaira Tadanao, and 10,000 other Easterners charged the barbican. The casualties were high amongst the attackers, but the Ii managed to get into the stockade, only to be shot to pieces, and assaulted by 8,000 under Kimura Shigenari, forcing the Easterners to withdraw. Ieyasu had no choice but to sit back and starve out the garrison with a long siege.

During the siege Ieyasu would bring up 300 cannon to bombard Osaka, while his miners dug under their defenses. Peace negotiations were opened with Hideyori, the terms of which were that he would retain possession of Osaka and the Tokugawa would withdraw, if Hideyori promised never to rebel again. Peace was signed January 22^nd.

However, many of the Tokugawa did not leave and began filling in the outer moat. Hideyori protested, since this had not been part of the agreement. Ieyasu stalled, and by the time he did draw his attention to the issue the outer moats had practically vanished.

With the coming of Spring, Hideyori ordered the moats to be re-excavated. Ieyasu took this as a sign that Hideyori was violating the treaty. This time some 120,000 had flocked to Hideyori's banner. Ieyasu assembled his forces, some 250,000 and marched back to Osaka.

In the Summer Campaign the Westerners would be the one to take the fight to the Tokugawa. They began by ambushing several contingents headed to Osaka. On April 29^th 3,000 Western troops under Ono Harunaga, Hanawa Naoyuki and Okabe Noritsuna marched on Wakayama castle held by Asano Nagaakira and 5,000 men. In the resulting battle at Kashii, the Westerners were forced to withdraw to Osaka, leaving behind several dead, including Hanawa and Okabe. After a council of war on May 2^nd it was decided that the Osaka garrison would go on the offensive. On May 6^th Goto Mototsugu with 2,800 men moved under cover of heavy fog to positions near Komatsuya. He soon bumped into 23,000 under Date Masumune, Mizuno Katsushige, Honda Tadamasa, and Matsudaira Tadaaki. Goto hastily withdrew to Mount Komatsu and awaited for help, but they could not find him in the fog. Goto and most of his contingent were destroyed. Meanwhile a new line was established along the Yamato river by 12,000 Westerners commanded by Mori Katsunaga and Sanada Yukimura. The Easterners crossed the river and attacked. Both sides withdrew after heavy casualties. The same day at Hachio 5,300 men under Chosokabe Morichika attacked Todo Takatora's 5,000, defeating them. Meanwhile at Wakae, Ii Naotaka with 4,700 men attacked Kimura Shigenari's 3,200, defeating them and killing Kimura. The next day the Westerners would commit everything in an all out attack against their adversary.

The plan for the Westerners was to make a frontal attack against the Eastern lines, while Akashi Morishige moved around the Tokugawa to attack in the rear. When this attack materialized, Hideyori was to lead his troops out of the castle bearing his fathers 'thousand gourd' standard. For this task 55,000 were assembled. On Chausuyama was positioned the commander, Sanada Yukimura, with 3,500 men. Behind him was Ebara Takatsugu with 1,000. To the left of Sanada was Yoshida's 1,000, Mori Katsunaga's 4,000, and Kimura Muneaki's 2,000 men. In front of Kimura were Asai Nagafusa and Takeda with 800 men. Positioned behind this main body was a series of reserves stretching to the outer moat: Ono Harunaga's 1,000, Shingu Yukitomo's and Fuse Denzaemon's 4,000, and 4,000 under Mishuku Masatomo, Ninomiya Naganori, Okabe Noritsuna, Kitagawa Norikatsu, Yamakawa Katanobu, and Ono Harufusa. A 'mobile' force of 14,200 stood ready between these reserves and the front line units. Akashi with approximately 16,500 was en route to attack the Tokugawa in the rear. Hideyori with 3,000 awaited in Osaka.

Ieyasu placed in overall command his son, Hidetada. The Easterners, some 155,000 strong, set up in a series of defensive lines. In the first line, directly opposite of Sanada's, was Akita and 1,000 men. To the right of his position was Asano Nagashige's 1,000, Honda Tadatomo's 1,000, and Sanada Nobuyoshi's 2,300. The second line of defense had 5,200 Echizen levies, behind which was positioned Matsudaira Tadanao with 7,800 men. Flanking them to the right was Suwa Tadazumi's 500, Sakakibara Yasukatsu's 2,000, Hoshina Masamitsu's 600, and Ogasawara Hidemasa's 1,600. The third line of defense consisted of Date Masumune's 10,000, who took position on the Kishu road. Behind him was Mizuguchi Norikatsu's 1,000, Murakami Yoshiaki's 1,800, and Matsudaira Tadateru's 9,000. Far to the right of them was positioned Hori Naoyaori with 600, Mizuno Katsushige's 600, and Honda Tadamasa's 2,000. To the right of them was Naito Tadaoki's 600, Matsudaira Yasunaga's 600, Sakai Ietsugu's 1,000, Matsudaira Tadayoshi's 800, and Sengoku Tadamasa's 1,000. The contingents of Matsudaira Tadaakira, Ichiryu Naomori, and Tokunaga Masashige formed behind this last line with approximately 3,000. On the right wing positioned near Okayama was Maeda Toshitsune, Katagiri Katsumoto, and Honda Yasunori with 15,000 men. behind them was a second line consisting of Ii Naotaka with 3,200, Hosokawa Tadaoki with 9,250, and Todo Takatora with 5,000. All four Tokugawa's stood in reserve with approximately 57,000 Hatamoto. Finally, Asano Nagakira with 10,000 men provided the rear guard. Ieyasu told his commanders to have all mounted troops dismount for the battle.

At noon the Westerners marched into view of the Easterners. Mori Katsunaga's ronin, without orders, immediately opened fire on the enemy vanguard. Sanada desperately tried to get them to stop, but it only made them want to increase their fire. His careful planning, which was to coincide with Akashi's flanking maneuver, had been thwarted by the eagerness of the ronin. Consulting with Mori, Sanada decided to go ahead and order the attack.

Immediately the order was sent down the lines. Mori led his men in a charge against the Tokugawa vanguard, breaking through them and continuing to the main body behind. Meanwhile, Sanada sent his son back to Osaka to tell Hideyori to march to the battle; he then led a charge into the Echizen levies. At the same time Asano Nagakira, without orders, moved his troops forward. This unexpected movement made many Easterners fear that Asano had turned traitor. In fact, Asano was only moving forward to reinforce the battle. Nevertheless, many Easterners began to panic and rout. Ieyasu moved forward to steady the men, and in doing so, came in contact with Sanada, who wounded him in the kidney with his spear. Date Masumune was able to get his men under control by shooting those who would not move (it turned out they were just tired). Soon his division was marching to support the main body.

Honda Tadatomo collected his men and led a charge into the flank of the Sanada, then together with the rallied main body, began pushing Sanada's men back towards Chausuyama. Sanada, exhausted after fighting for so long continuously, took some time to rest. A Samurai named Nishio Nizaemon saw him and issued a challenge, but Sanada was too tired to accept; news of his death was soon circulating throughout the ranks.

With the news of Sanada's death, the Easterners renewed their attacks. Mori's ronin were fighting like 'wildcats' and weren't giving up any ground. Hidetada sent orders to Ii and Todo to support the main body's efforts, but was soon recalling them because Ono Harunaga had decided to unleash the reserves against Hidetada. A call for help was also sent to Maeda, but received no reply (they hadn't finished lunch). Soon, Hidetada's Hatamoto was being pushed back. Ii immediately wheeled his troops and went to support, but were shot up badly by Ono's arquebusiers. If at that moment Akashi's men had materialized, it is certain that the Tokugawa would have routed. In any event the attack never came because while en route, Akashi's men had been intercepted. Maeda, having finished his lunch, now attacked the Westerners, who soon broke and fled.

The Tokugawa followed the fleeing Westerners towards the castle. Hideyori had finally decided to come out and fight, but it was too late; he too fled into the castle. While Mizuno planted his standard on the Sakura gate, the Tokugawa artillery moved forward and bombarded the castle, which was soon in flames. Breaking through the Sakura gate, the Easterners moved into the castle. By 5 P.M. the castle was Ieyasu's.

Throughout the night the bombardment continued against those who took shelter in the Keep. Hideyori knew his time was up and committed suicide along with his family. After the battle, Hideyori's eight-year-old son, the last of the Toyotomi was beheaded. The final battle had been won, and no more would the Toyotomi arise to challenge Tokugawa authority. Ieyasu was now complete master of Japan.