Hamamatsu Castle, Ieyasu's Journey of Building a Peaceful Era

Tokugawa Ieyasu (1543-1616, 徳川家康) was freed from his hostage of Imagawa Yoshimoto (1519-1560, 今川義元) defeated at the Battle of Okehazama, and took a step forward as the lord of Okazaki Castle. He put down the Mikawa Ikki riot and brought stability to the Mikawa region in 1645. Following the surrender of the Imagawa clan's Sunpu Castle in 1569, Ieyasu relocated his base from Okazaki to Hamamatsu Castle in 1570, situated at the center of the Mikawa region. Despite securing the west through an alliance with Oda Nobunaga (1534-1582, 織田信長), the Eastern area was the scene of repeated clashes among the prominent warlords of the Warring States period. To the east, neighboring Mikawa was Takeda Shingen (1521-1573, 武田信玄), renowned as the "Tiger of Kai"; to the Kanto region, Hojo Ujiyasu (1515-1571, 北条氏康) feared as the "Lion of Sagami"; and to the north, Uesugi Kenshin (1530-1578, 上杉謙信), a famous general revered as the military deity, Bishamonten.

A Big Defeat by Takeda Shingen

In 1572, Takeda Shingen invaded the Mikawa region, crossing the Oi River with a formidable army of 25,000 men. In a fierce battle, the subsidiary castles of the Tokugawa Ieyasu were defeated. Honda Tadakatsu (1548-1610, 本田忠勝), known as Heihachiro, wearing a deer horn Kabuto helmet, defended the rear and eventually managed to retreat to Hamamatsu Castle despite considerable difficulty. Shingen praised Heihachiro's bravery, remarking, "Heihachiro is too good for Ieyasu to have. Shingen's march continued relentlessly.

Following Tokugawa's Futamata Castle fell by Shingen's fierce attack, he headed for Hamamatsu Castle. However, the Takeda forces passed through Hamamatsu Castle and proceeded toward Mikatagahara Field, seemingly in disdain of the Tokugawa forces. Ieyasu pursued Shingen amidst the prevailing sentiment that a warlord who could not fight would lose credibility. Although he probably did not intend to go in-depth, it seems that, by accident, a full-scale battle ensued. (There is a different theory that Ieyasu pursued Shingen, over the objections of his retainers, saying, “We cannot allow Shingen's forces to pass through our territory.) Just before descending the Mikatagahara Plateau, Shingen turned his forces and executed a strategic position of his entire army in a magnificent formation to confront Ieyasu's forces head-on. The Tokugawa forces suffered a crushing defeat at the hands of Shingen's army, resulting in the loss of numerous vassals and retreat to Hamamatsu Castle. After that, Shingen continued his westward advance, and Okazaki Castle might have fallen. Suddenly, however, Takeda's army halted its progress and withdrew to Shingen's stronghold. Shingen died of illness. It could be said that fortune sided with Ieyasu.

Victory against the Rival, the Takeda clan

Shingen's passing ignited a conflict between Ieyasu, intent on recovering authority in Mikawa, and Shingen's heir, Katsuyori. Ieyasu successfully retook Nagashino Castle, the critical stronghold in Takeda's Mikawa campaign, while Katsuyori seized Takatenjin Castle in response. Subsequently, Katsuyori sought to recapture Nagashino Castle, marking the start of the Battle of Nagashino & Shitaragahara, a turning point in history.

The balance shifted when Sakai Tadatsugu, Ieyasu's chief vassal known for his strategic eye and intimate knowledge of Nagashino Castle’s terrain. He attacked the Tobigasuzu fort overlooking Nagashino Castle, which Katsuyori had built, from the rear. This attack forced the Takeda forces into a dangerous position to be caught between the two armies. Having no choice, the Takeda forces charged toward the Oda and Tokugawa armies, where 1,000 or more guns awaited. It proved to be the moment when fortune favored Oda and Tokugawa. Unified, Oda and Tokugawa forces attacked the Takeda's brave and strong cavalry with relentless gunfire. Tokugawa's gunmen fought hard in front of the horse-proof fence. Furthermore, Tokugawa’s vassal, Naruse Masakazu, spotted the banner of Takeda's generals and directed Oda and Tokugawa gunmen to take shots targetting them. Masakazu's heir would later become the lord of Inuyama Castle of Tokugawa Owari domain.

Behind this great victory lay plentiful ammunition, surpassing that of the Takeda army. The large quantities of gunpowder and gun balls from overseas, acquired through the Sakai, Osaka’s bustling merchant city, enabled Nobunaga and Ieyasu's forces to fire their guns relentlessly. Katsunori, on the other hand, did not sit idly by. He desperately manufactured ammunition by melting copper coins. However, he proved incapable of suppressing Oda and Tokugawa’s output, ultimately suffering a crushing loss in a hail of bullets. In 1581, Ieyasu decisively recaptured Takatenjin Castle, which Katsunori had taken. By February 1582, Ieyasu and Nobunaga launched an invasion of the weakened Takeda territory. The strongest Takeda clan in the Warring States period was destroyed.

A Three-Way Conflict Erupted in the Former Takeda Domain

Following a celebration of victory at the splendid Azuchi Castle built by Nobunaga, Ieyasu enjoyed Sakai city sights. It was there that he received news of Nobunaga's tragic death (Honnoji Incident), a result of a rebellion by one of his retainers. Faced with the threat of rebellion or hunts on fallen warriors, Ieyasu miraculously traversed back safely across the mountainous Iga to Okazaki Castle, protected by his loyal retainers and the wealthy merchant, Chaya Shirojiro, a supplier to the Tokugawa clan who safeguarded Ieyas by scattering gold coins to discourage potential attacks. Upon their return, the Tokugawa, Uesugi, and Hojo clans engaged in a fierce four-month struggle for control amid the power vacuum in the former Oda domain, once held by Takeda territory. Ieyasu entered into Kofu (Yamanashi), the center of the former Takeda territory, initiating negotiations to let the former Takeda vassals belong to the Tokugawa faction. Notably, the 22-year-old Ii Naomasa played a key role in this diplomatic process. Eventually, a peace agreement was reached, with Ieyasu taking the southern portion of Kai and Shinano, the Hojo clan securing Ueno, and the Uesugi clan claiming the northern area of Shinano. Naomasa was also responsible for negotiating peace with the Hojo clan.

Komaki-Nagakute Battle against Hideyoshi

In 1584, the Tokugawa forces clashed with the Toyotomi forces in Komaki & Nagakute in support of Nobukatsu, the second son of Nobunaga, who was dissatisfied with the power grab by Nobunaga's vassal, Toyotomi Hideyoshi, over the Oda family after the Honnoji incident. When the Toyotomi forces seized the fortified Inuyama Castle on a steep hill along the Kiso River, the Oda and Tokugawa forces entered Komakiyama Castle on a freestanding mountain near Inuyama Castle. With only 2 km between the two castles. Toyotomi's 100,000-strong army could not attack carelessly in the face of the Tokugawa and Oda forces, and a standoff ensued between the two sides, leading to a stalemate. To break the deadlock, Hideyoshi launched an attack on Okazaki Castle, the Tokugawa stronghold. Ieyasu, however, was a notch above Hideyoshi. Ieyasu left his main camp of Komaki Castle, and together with a detachment, Tokugawa forces pinched Hideyoshi's forces and destroyed them. However, as Nobukatsu had reconciled with Hideyoshi, Ieyasu deemed further battles unnecessary and withdrew to Hamamatsu Castle. Subsequently, Ieyasu and Hideyoshi engaged in diplomatic war rather than direct conflicts on the battlefield.

There is one episode. During the battle, Ieyasu's chief vassal, Sakakibara Yasumasa (1548-1606, 榊原康正), proclaimed, "Hideyoshi is attempting to control the Oda family." In response, Hideyoshi placed a bounty on Yasumasa. Under Ieyasu’s leadership, there existed a vassal characterized by boldness and courage, who demonstrated a willingness to risk his life in pursuit of the Tokugawa’s ambition. (Source: "Buya Shokudan" 武野燭談)

The End of the Tumultous Warring States Period

In 1585, Hideyoshi assumed the position of Kanpaku (Chief advisor to the emperor) and gradually brought his opponents under his control, leveraging the backing of the emperor. Finally, even Ieyasu decided to serve Hideyoshi. In 1590, Hideyoshi compelled the Hojo clan to surrender Odawara Castle, thereby achieving national unification and effectively bringing an end to the tumultuous Warring States period that had lasted for over 120 years.

150 Letters Brought the Victory to Ieyasu

Following Hideyoshi’s death in 1598, Ieyasu began taking a more independent course, entering into conflict with Ishida Mitsunari (1560-1600, 石田三成) who remained loyal to Hideyori, Hideyoshi's eldest son.

The pivotal battle of Sekigahara occurred on October 21, 1600, splitting Japan’s feudal lords into two factions and determining the nation’s next ruler. The battle ended in victory for the Tokugawa in just a few hours. Ieyasu's skillful control of people's hearts and minds shone through in this victory. The decisive factor in securing victory lay in persuading warlords aligned with the Toyotomi faction to switch their minds to the Tokugawa side. To this end, Ieyasu tasked Ii Naomasa with recruiting the Mori clan, the enemy's formidable force, to join the Tokugawa side, and it was accomplished just before the battle. Additionally, Ieyasu dispatched 82 feudal lords and over 150 letters within 50 days, urging them to align with the Tokugawa cause. These massive letters promised territorial rewards for those loyal to the Tokugawa in the event of victory, who were swaying their minds between loyalty to the Toyotomi and the Tokugawa. On the other hand, Ishida Mitsunari preached "righteousness" in his letters to follow the Toyotomi family. Ieyasu, who loved to read "Rikuto" (an ancient Chinese strategy book), which advocated that "the relationship between sovereign and vassal is based on the calculation of interests," took up the challenge of fighting for supremacy as a feudal lord in the Warring States Period. It is fair to say that Ieyasu could win the war thanks to these letters and Naomasa's success in recruiting the Mori clan to the Tokugawa side.

Ieyasu's vision of a Peaceful Era was Realized

In 1603, Ieyasu ascended to shogun, establishing the Tokugawa shogunate in Edo, known today as Tokyo. Concurrently, Toyotomi Hideyori, Hideyoshi's heir, grew up healthy in the solid Osaka Castle and became a young warrior who would carry the future Toyotomi family on his shoulders. Numerous warlords aligned with the Toyotomi faction during the Battle of Sekigahara confiscated their fiefdoms and were left without a lord, rallying under Hideyori’s banner to restore their lost status. This raised the tensions between Ieyasu and the Toyotomi family again. In 1614, the winter campaign of the Siege of Osaka began. Efforts at reconciliation were made by Oda Nagamasu (1548-1622, 織田長益・有楽斎), Nobunaga's younger brother, and Achano-no-Tsubone, Ieyasu's second wife, who successfully made peace at Osaka Castle between Toyotomi and Tokugawa clans. However, these efforts proved futile. In 1615, Osaka Castle fell in flames, and both Hideyori and his mother, Yodo-dono, tragically committed suicide. With no feudal lord capable of challenging the formidable military might and authority of the Tokugawa, Ieyasu's vision of an era characterized by peace was realized. His subsequent mission was to solidify the Tokugawa shogunate as a robust organization and transition governance from a military-centric to a civil-oriented structure.

Tokugawa Ieyasu Timeline

1570	Ieyasu moved to Hamamatsu Castle from Okazaki Castle	29	Muromachi Period
1572	The battle of Mikatagahara	31
1573	Muromachi Shogunate ended by the 15th Shogun	31	Azuchi-Momoyama Period
1575	The battle of Nagashino & Shitaragahara. Takeda clan ended	34
1582	Nobunaga invited Ieyasu at Azuchi Castle	41
1582	Nobunaga was killed at Honnoji by Akechi Mitsuhide	41
1582	Ieyasu returned to Okazaki Castle through crossing the pathless Iga route	41
1582	Hideyoshi defeated Akechi Mitsuhide	41
1584	Komaki-Nagakute battle between Hideyoshi and Ieyasu	43
1585	Hideyoshi became Kanpaku (chief advisor to the Emperor)	44
1586	Hideyoshi built the huge Osaka castle	45
1590	Hideyoshi spearhead army to attack Hojo clan	49
1590	Hideyoshi unified the nation	49
1590	Ieyasu moved to Edo according to Hideyoshi's order	49
1598	Hideyoshi passed away	57
1600	The Battle of Sekigahara. Tokugawa Ieyasu defeated Ishida Mitsunari	59

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