Oda Nobunaga, one of the first of Japan's "three unifiers," was a strong and influential fighter who emerged from a century-long civil war as the most powerful daimyo in the land.

Japan was rife with internal conflict in the Middle Ages, most notably for more than a century in the Sengoku ("Warring States") period, which spanned the late 15th Century and much of the 16th Century. The fighting ranged throughout the various islands. Reigning (at times in name only) over all of this conflict were the Ashikaga shogunate, who had a strong history but a long and languishing decline.

One of the most forceful personalities during the mid-16th Century fighting was Oda Nobunaga. Born on June 23, 1534, he was the inheritor of the fortune and power of the Oda, one of Japan's most influential clans at the time. The head of the Oda at the time of Nobunaga's birth was Oda Nobuhide.

Nobunaga grew up in the shadow of the Sengoku fighting. As the son of a military man, he learned the useful habits of hunting, riding, and shooting. A strong athlete, the young Nobunaga proved a skillful swimmer and wrestler. He was expected to take over the clan when his father died, so he enjoyed dedicated learning from a group of four teachers. At the same time, Nobunaga struck back at conventions, refusing to wear the clothing that his parents and wider conventions demanded, and exhibited well-known instances of strange behavior.

He lived at Nagoya Castle and then, aged 21, moved to Kiyosu Castle. He married Nohime, daughter of a rival lord, in a political marriage designed to keep the peace.

Oda Nobuhide died in 1551, and Nobunaga assumed leadership of the clan. It was not without incident, however, because some Oda disputed Nobunaga's ascendancy, citing his bizarre behavior, a recent example of which was allegedly defiling his father's funeral altar. The succession crisis deepened as his powerful uncle Nobutomo joined the fray, attacking Nobunaga's lands. The young warlord found his way to a strong victory and took the battle to Nobutomo, burning bits of his castle in the process.

Nobunaga was also battling against the powerful Imagawa clan, and he achieved a strong victory over them at the Battle of Muraki Castle, in 1554. He had let his uncle live, with the promise that he wouldn't challenge Nobunaga further; Nobutomo reneged on that promise, and Nobunaga had the final victory. It was the latest in a string of triumphs that resulted, by 1558, in the elimination of all resistance and, therefore, his complete domination of the Oda clan.

The Imagawa were nowhere near finished, however, and in 1560 marched on Kyoto, the capital city, with an army numbering in the tens of thousands. Nobunaga had a much smaller force but was determined to defend the capital. He caught the Imagawa forces unawares, at first fooling them with a decoy army and then launching an attack directly after a fierce thunderstorm. Nobunaga won a great victory, killing the Imagawa leader, Yoshimoto, in the process.

Open to new ways of thinking and fighting, Nobunaga welcomed the contribution of an earlier Portuguese delegation: firearms. He also studied the military tactics introduced by the Portuguese, whose numbers included a number of Jesuit missionaries and the explorer Mendez Pinto.

Nobunaga was gaining in fame and fortune, and he now had military successes to match. The year after he dispatched Yoshimoto, Nobunaga entered into an alliance with two other powerful daimyo, Matsudaira Motoyasu and Takeda Shingen. Nobunaga also enjoyed the support and services of Toyotomi Hideyoshi, a brilliant fighter, diplomat, and leader.

Flush with success, Nobunaga expanded his campaign against other daimyo, setting up a base at Komaki Castle and moving into more provinces. To help facilitate his expansion, he had built Sunomata Castle, in a strategic location at the confluence of two rivers.

In 1567, Nobunaga got some unexpected aid, in the form of a trio of samurai who had served the Saito clan but moved over to Nobunaga's forces and helped him achieve the defeat of the Saito, at the Siege of Inabayama Castle. This resulted in Nobunaga's capture of the powerful Mino province.

In the next two years, Nobunaga further solidified his power by sending subordinates to do battle for him, achieving victories in neighboring provinces, and marrying off female relatives to other powerful warlords to solidify alliances.

All of this time, the Ashikaga shogunate were nominally the leaders of Japan. They were, however, a string of weak leaders who did nothing to stop the fighting and benefited little from either side. That changed in 1568, when Ashikaga Yoshiaki asked Oda Nobunaga for support. Yoshiaki's brother, Yoshiteru, had been shogun but was assassinated by members of the Miyoshi clan and replaced by their hand-picked successor, Yoshihide. Nobunaga agreed to support Yoshiaki's claim to succeed his brother and marched at the head of a large force for Kyoto. After a few setbacks, Oda Nobunaga entered Kyoto in triumph, installing Yoshiaki as the legitimate shogun.

Yoshiaki named Nobunaga as his deputy, but the warlord refused. He had other ideas, preferring to further his campaign to defeat rival clans. In 1570, he targeted Kanagasaki Castle and the Asakura clan. The shogun retaliated by forging a secret alliance, including both the Asakura and Azi clans, to dispatch Nobunaga.

By that time, Nobunaga had renewed his alliance with Matsudaira Motoyasu, who by that time had power and many men under his control. The allies confronted the Asakura-Azi force at the Battle of Anegawa and were victorious. Nobunaga continued to pursue his enemies, finally ending their resistance in 1573.

At the same time, Nobunaga was fighting on another front, against the Ikko-ikki, a Buddhism-inspired resistance movement. This struggle lasted much longer, stretching into 1580. Finally, Nobunaga's siege of Ishiyama Hongan-ji ended in his enemies' capitulation.

By that time, one of Nobunaga's former allies had turned against him. Takeda Shingen, who had entered into an alliance with Nobunaga earlier, saw an opportunity and made a move on Kyoto. Nobunaga could still count on the aid of another ally, Matsudaira Motoyasu, who joined the fray in 1573 (and by that time had become Tokugawa Ieyasu). That support was enough to blunt the attack, for a time. After Shingen died, his son Takeda Katsuyori carried on the attack, targeting Matsudaira territory, including a siege of Nagashino Castle. Nobunaga, freed after winning his own battles, sent a large mass of troops to help his ally; the result was a Nobunaga victory at the Battle of Nagashino.