Rise to power (1556–1584)
In
1556, Ieyasu came of age, and, following tradition, changed his name to Matsudaira Jirōsaburō Motonobu (松平次郎三郎元信). One year later, at the age of 16 (according to
East Asian age reckoning), he married his first wife and changed his name again to Matsudaira Kurandonosuke Motoyasu (松平蔵人佐元康). Allowed to return to his native Mikawa, the Imagawa ordered him to fight the Oda clan in a series of battles. Ieyasu won his first battle at the
Siege of Terabe and later succeeded in delivering supplies to a border fort through a bold night attack.
In
1560 the leadership of the Oda clan had passed to the brilliant leader
Oda Nobunaga. Yoshimoto, leading a large Imagawa army (perhaps 20,000 strong) then attacked the Oda clan territory. Ieyasu with his Mikawa troops captured a fort at the border and then stayed there to defend it. As a result, Ieyasu and his men were not present at the
Battle of Okehazama where Yoshimoto was killed by Oda Nobunaga's surprise assault.
With Yoshimoto dead, Ieyasu decided to ally with the Oda clan. A secret deal was needed because Ieyasu's wife and infant son,
Nobuyasu were held hostage in Sumpu by the Imagawa clan. In
1561, Ieyasu openly broke with the Imagawa and captured the fortress of Kaminojo. Ieyasu was then able to exchange his wife and son for the wife and daughter of the ruler of Kaminojo castle.
For the next few years Ieyasu set about reforming the Matsudaira clan and pacifying Mikawa. He also strengthened his key vassals by awarding them land and castles in Mikawa. They were:
Honda Tadakatsu, Ishikawa Kazumasa, Koriki Kiyonaga, Hattori Hanzō, Sakai Tadatsugu, and
Sakakibara Yasumasa.
Ieyasu defeated the military forces of the Mikawa Monto within Mikawa province. The Monto were a warlike group of monks that were ruling
Kaga Province and had many temples elsewhere in Japan. They refused to obey Ieyasu's commands and so he went to war with them, defeating their troops and pulling down their temples. In one battle Ieyasu was nearly killed when he was struck by a bullet which did not penetrate his armor. Both Ieyasu's Mikawa troops and the Monto forces were using the new gunpowder weapons which the Portuguese had introduced to Japan just 20 years earlier.
In
1567, Ieyasu changed his name yet again, his new
surname was
Tokugawa and his personal name was now
Ieyasu. In so doing, he claimed descent from the
Minamoto clan. No proof has actually been found for this claimed descent from
Seiwa tennō, the 56th Emperor of Japan.
Ieyasu remained an ally of Oda Nobunaga and his Mikawa soldiers were part of Nobunaga's army which captured
Kyoto in
1568. At the same time Ieyasu was expanding his own territory. He and
Takeda Shingen, the head of the
Takeda clan in
Kai Province made an alliance for the purpose of conquering all the Imagawa territory. In
1570, Ieyasu's troops captured
Tōtōmi Province while Shingen's troops captured
Suruga province (including the Imagawa capital of Sumpu).
Ieyasu ended his alliance with Takeda and sheltered their former enemy,
Imagawa Ujizane; he also allied with
Uesugi Kenshin of the Uesugi clan—an enemy of the Takeda clan. Later that year, Ieyasu led 5,000 of his own men supporting Nobunaga at the
Battle of Anegawa against the
Asai and
Asakura clans.
In October
1571, Takeda Shingen, now allied with the
Hōjō clan, attacked the Tokugawa lands of Tōtōmi. Ieyasu asked for help from Nobunaga, who sent him some 3,000 troops. Early in
1572 the two armies met at the
Battle of Mikatagahara. Nobunaga's troops fled early and the Takeda army, under the expert direction of Shingen, hammered at Ieyasu's remaining troops till they were broken. Ieyasu fled with just 5 men to a nearby castle. This was a major loss for Ieyasu, but Shingen was unable to exploit his victory because Ieyasu quickly gathered a new army and refused to fight Shingen again on the battlefield.
Fortune smiled on Ieyasu a year later when Takeda Shingen died at a siege early in
1573. Shingen was succeeded by his less capable son
Takeda Katsuyori. In
1575, the Takeda army attacked Nagashino Castle in Mikawa province. Ieyasu appealed to Oda Nobunaga for help and the result was that Nobunaga personally came at the head of his very large army (about 30,000 strong). The Oda-Tokugawa force of 38,000 won a great victory on
June 28, 1575, at the
Battle of Nagashino, though Takeda Katsuyori survived the battle and retreated back to Kai province.
For the next seven years, Ieyasu and Katsuyori fought a series of small battles. Ieyasu's troops managed to wrest control of Suruga province away from the Takeda clan.
In
1579, Ieyasu's wife, and his eldest son,
Matsudaira Nobuyasu, were accused of conspiring with Takeda Katsuyori to assassinate Nobunaga. Ieyasu's wife was executed and Nobuyasu was forced to commit
seppuku. Ieyasu then named his third and favorite son,
Tokugawa Hidetada, as heir, since his second son was adopted by another rising power:
Toyotomi Hideyoshi, the future ruler of all Japan.
The end of the war with Takeda came in
1582 when a combined Oda-Tokugawa force attacked and conquered Kai province. Takeda Katsuyori, as well as his eldest son Takeda Nobukatsu, were defeated at the
Battle of Temmokuzan and then committed
seppuku.
In late
1582, Ieyasu was near
Osaka and far from his own territory when he learned that Oda Nobunaga had been assassinated by
Akechi Mitsuhide. Ieyasu managed the dangerous journey back to Mikawa, avoiding Mitsuhide's troops along the way, as they were trying to find and kill him. One week after he arrived in Mikawa, Ieyasu's army marched out to take revenge on Mitsuhide. But they were too late, Hideyoshi—on his own—defeated and killed Akechi Mitsuhide at the
Battle of Yamazaki.
The death of Oda Nobunaga meant that some provinces, ruled by Nobunaga's vassels, were ripe for conquest. The leader of Kai province made the mistake of killing one of Ieyasu's aides. Ieyasu promptly invaded Kai and took control.
Hōjō Ujimasa, leader of the Hōjō clan responded by sending his much larger army into
Shinano and then into Kai province. No battles were fought between Ieyasu's forces and the large Hōjō army and, after some negotiation, Ieyasu and the Hōjō agreed to a settlement which left Ieyasu in control of both Kai and Shinano provinces, while the Hōjō took control of Kazusa province (as well as bits of both Kai and Shinano province).
At the same time (
1583) a war for rule over Japan was fought between
Toyotomi Hideyoshi and
Shibata Katsuie. Ieyasu did not take a side in this conflict, building on his reputation for both caution and wisdom. Hideyoshi defeated Katsuie at the
Battle of Shizugatake—with this victory, Hideyoshi became the single most powerful
daimyo in Japan.