He just needed to name an heir.

Ashikaga Yoshimasa, the eighth Ashikaga shogun, had many qualities that made him exceptional — a refined aesthetic sensibility, deep knowledge of tea ceremony, a genuine gift for the arts of what would become known as Higashiyama culture (Higashiyama bunka). Governing a nation was not among his gifts. He disliked politics. He disliked conflict. He disliked, most of all, the relentless pressure of being the man in the room who was expected to decide things.

In 1464, he had no heir and named his younger brother Ashikaga Yoshimi as successor. In 1465, his wife Hino Tomiko gave birth to a son, Yoshihisa. Two heirs. One shogun who would not choose between them.

The vacuum his indecision created was catastrophic.

On one side stood Hosokawa Katsumoto, the kanrei (kanrei) — the shogun's deputy, the most administratively powerful man in Japan — who backed Yoshimi and his Eastern Army. On the other side stood Yamana Sōzen, Katsumoto's own father-in-law, a man who controlled eleven of Japan's sixty-six provinces — roughly one-sixth of the entire country, earning him the nickname 'the sixth-part lord.' Yamana led the Western Army for young Yoshihisa, urged on by Hino Tomiko, who wanted the shogunate for her son and was willing to use whatever leverage she had to get it.

In the first month of 1467, both armies — each numbering approximately 80,000 men, according to the traditional accounts — assembled within the streets and neighborhoods of Kyoto. The city had been Japan's imperial capital since 794, a place of centuries-old aristocratic culture, great Buddhist temples, and Shinto shrines. It was not built to absorb two armies.

The fighting was urban. Mansions became fortresses. Streets became killing grounds. Fire was a constant weapon on both sides. The great cultural landmarks of the Heian and Kamakura periods — palaces, temples, the sprawling estates of nobles who had cultivated the arts for generations — burned. The aristocracy fled.

Neither side won. Yamana Sōzen died of illness in 1473. Hosokawa Katsumoto died that same year, also of illness, also without resolution. The war continued, increasingly directionless, until it simply exhausted itself in 1477. Kyoto lay in ruins. The Ashikaga shogunate still technically existed, but its authority had been stripped away province by province as regional daimyo (daimyo) stopped obeying anyone and began seizing what they could hold.

The Sengoku period — the 'Warring States' era, roughly 1467–1615 — had begun. It would produce Oda Nobunaga, Toyotomi Hideyoshi, and Tokugawa Ieyasu. Every one of those men was filling the vacuum the 応仁の乱 (Ōnin no Ran) created.

Hino Tomiko, the woman who helped ignite the war by pressing for her son's succession, did not suffer greatly from the catastrophe she helped cause. According to some accounts, she lent money to both sides of the conflict, accumulating a substantial personal fortune while the capital burned around her. After 1473, with both warlords dead, she became the de facto political power behind the shogunate — a remarkable position for a woman in medieval Japan, built on the ruins of the city she had helped destroy.

Yoshimasa, for his part, retired. He designed 銀閣寺 (Ginkaku-ji) — the Silver Pavilion — and refined the aesthetic traditions of tea, flower arranging, and Noh drama that would come to define Japanese court culture for centuries. The man who could not settle a succession question left behind some of the most enduring cultural institutions in Japanese history.

It is not easy to know what to make of Yoshimasa. He was genuinely gifted in the arts he pursued. He was genuinely incapable of the political will that his position demanded. The 応仁の乱 (Ōnin no Ran) — the 'Ōnin Disturbance' — is in part his monument: proof that the most devastating war in medieval Japanese history can be started not by ambition, not by ideology, not by territorial hunger, but simply by a man who could not bring himself to make a decision.