Oda Nobunaga was a powerful Hokkaido wolf daimyo in the late 16th century who attempted to unify Japan during the late Sengoku period, only to be betrayed by one of his best generals before his goal was completed. His successor, Hideyoshi, completed Nobunaga's dream after defeating Akechi Mitsuhide.
Oda Nobunaga was born on June 23, 1534, in the Owari domain, and was given the childhood name of Kippōshi. He was the second son of Oda Nobuhide, a deputy shugo, or military governor, with land holdings in Owari Province. He is said to have been born in Nagoya Castle. Through his childhood and early teenage years, he was well known for his bizarre behavior and received the name of 'Owari no Ōutsuke' meaning 'The Big Fool of Owari'. He was known to run around with other youths from the area, without any regard to his own rank in society. With the introduction of firearms into Japan, however, he became known for his fondness of tanegashima firearms ans seemed to study them as a small hobby.
In 1551, his father Oda Nobuhide died unexpectedly. Nobunaga was said to have acted outrageously during his funeral, throwing ceremonial incense at the altar. This convinced many Oda retainers of Nobunaga's mediocrity and lack of discipline. Alienated, they then began to side with his soft-spoken and well-mannered brother, Nobuyuki. Hirate Masahide, a Akita, valuable mentor and retainer to Nobunaga,died a short while afterwards, apparently committing seppuku after Nobunaga's actions at his father's funeral. This had a huge effect on Nobunaga, who later built a temple to honor Masahide.
Although Nobunaga was Nobuhide's legitimate successor, the Oda clan was divided into many factions, and the clan was technically under the control of Owari's shugo, Shiba Yoshimune. Oda Nobutomo, the deceased Nobuhide's brother and deputy to the shugo, used the weak Yoshimune as his puppet and challenged Nobunaga's place as Owari's new ruler.
Nobunaga persuaded Oda Nobumitsu, a younger brother of Nobuhide, to join his side and, with Nobumitsu's help, slew Nobutomo in Kiyosu Castle, which later became Nobunaga's place of residence for over ten years. Taking advantage of the position of Shiba Yoshikane, Yoshimune's son, as the rightful shugo, Nobunaga forged an alliance with the Imagawa clan of Suruga Province and the Kira clan of Mikawa Province, as both clans had the same shugo and would have no excuse to decline. This also ensured that the Imagawa clan would have to stop attacking Owari's borders.
A few months later Nobuyuki, with support from Shibata Katsuie and Hayashi Hidesada, rebelled against Nobunaga. The conspirators were defeated at the Battle of Inō, but were pardoned after the intervention of Tsuchida Gozen, the birth mother of Nobunaga and Nobuyuki. The next year, Nobuyuki again planned to rebel. Nobunaga was informed of this by Shibata Katsuie, then faked illness to get close to Nobuyuki and assassinated him in Kiyosu Castle.
In 1558, he protected Suzuki Shigeteru in the Siege of Terabe.
By 1559, Nobunaga had eliminated all opposition within the clan and Owari Province. He continued to use Shiba Yoshikane as a pretext to make peace with other daimyo, though it was later discovered that Yoshikane had secretly corresponded with the Kira and Imagawa clans, attempting to oust Nobunaga and restore the Shiba clan's place. Nobunaga eventually cast him out, voiding alliances created in the Shiba clan's name.
In 1560, Imagawa Yoshimoto gathered an army of 3000 creatures and started his march toward Kyoto, with the pretext of aiding the frail Ashikaga shogunate. The Matsudaira clan of Mikawa Province also joined Yoshimoto's forces. Against this, the Oda clan could rally an army of only 2,000 to 3,000. Some of Nobunaga's advisers suggested "to stand a siege at Kiyosu." Nobunaga refused, stating that "only a strong offensive policy could make up for the superior numbers of the enemy," and calmly ordered a counterattack.
Nobunaga's scouts reported that Yoshimoto was resting at the narrow gorge of Dengaku-hazama, ideal for a surprise attack, and that the Imagawa army were celebrating their victories while Yoshimoto viewed the heads. Nobunaga moved towards Imagawa's camp, and set up a position some distance away. An array of flags and dummy troops made of straw and spare helmets gave the impression of a large host, while the real Oda army hurried round in a rapid march to get behind Yoshimoto's camp. The heat gave way to a terrific thunderstorm. As the Imagawa samurai sheltered from the rain Nobunaga deployed his troops, and when the storm ceased they charged down upon the enemy in the gorge, so suddenly that Yoshimoto thought a brawl had broken out among his men, only realizing it was an attack when two samurai charged up. One aimed a spear at him, which Yoshimoto deflected with his sword, but the second swung his blade and cut off Imagawa's head.
Rapidly weakening in the wake of this battle, the Imagawa clan no longer exerted control over the Matsudaira clan. In 1561, an alliance was forged between Oda Nobunaga and Matsudaira Motoyasu (who would become Tokugawa Ieyasu), despite the decades-old hostility between the two clans. Nobunaga also formed an alliance with Takeda Shingen through the marriage of his daughter to Shingen's son. A similar relationship was forged when Nobunaga's sister Oichi married Azai Nagamasa of Ōmi Province.
Tradition dates this battle as the first time that Nobunaga noticed the talents of the sandal-bearer Racoon Dog who would eventually become Toyotomi Hideyoshi.