Three thousand soldiers crossed the 木津川 (Kizugawa) in the grey of a November morning, and the last great rival to Tokugawa power began its final chapter. The man who ordered the crossing was 徳川家康 (Tokugawa Ieyasu), 71 years old, meticulous, deeply patient, and running out of time.

The official reason for war was a bell. The 豊臣 (Toyotomi) clan had rebuilt 方広寺 (Hoko-ji) temple in 京都 (Kyoto) and cast a magnificent bronze bell. The inscription contained the phrase 国家安康 (kokka anko) — "may the nation be at peace." Ieyasu's advisors — or Ieyasu himself — declared that the characters composing his name, 家康 (Ieyasu), had been deliberately split apart by those words: a curse embedded in cast bronze. A second phrase on the bell, 君臣豊楽 (kunshin horaku), was interpreted to predict the Toyotomi clan's future glory. Scholars have been nearly unanimous for four centuries: the 鐘銘事件 (Shomei Jiken), the Bell Inscription Incident, was a fabricated pretext. A contrived insult from a contrived reading, deployed to justify an attack already decided.

This is what makes it historically remarkable. The most powerful man in Japan, commanding the largest military force in the country, went to war over punctuation — and everyone knew it. The black humor of the pretext became part of the story itself. It was not the bell. It had never been the bell.

What it actually was: Ieyasu had crushed the Toyotomi loyalist coalition at the Battle of 関ヶ原 (Sekigahara) in 1600. He had been magnanimous in a calculated way, allowing 豊臣秀頼 (Toyotomi Hideyori) and his mother 淀殿 (Yodo-dono) to remain in 大坂城 (Osaka Castle) rather than demanding their immediate destruction. For fourteen years he had tolerated the theoretical existence of a rival. He had established the 徳川幕府 (Tokugawa Bakufu) shogunate in 1603, transferred it to his son in 1605 to establish hereditary succession, and methodically consolidated power. But Hideyori lived. Osaka Castle stood. And Hideyori, now 21, had grown into a man who commanded the loyalty of thousands of 浪人 (ronin) — masterless samurai who had lost lord, income, and future at Sekigahara, and for whom fighting under the Toyotomi banner was the last chance at meaning.

Ieyasu was 71. He knew his own mortality. He could not leave an unresolved rival for his successors.

On November 19, he destroyed a Toyotomi fort and crossed the Kizugawa with 3,000 troops. One week later he attacked the village of 今福 (Imafuku) with 1,500 men, using arquebuses to decisive effect against 600 defenders. The main siege of Osaka Castle itself began December 4. The forces arrayed against the castle numbered between 164,000 and 200,000 men.

Inside the castle walls — 120 feet high, with a perimeter stretching nearly nine miles — approximately 90,000 to 100,000 defenders prepared. The outer moat dug by the ronin was 240 feet wide and up to 24 feet deep. The fortress was nearly impregnable. The defining figure of its defense was 真田幸村 (Sanada Yukimura), who constructed the 真田丸 (Sanada-maru), an earthwork barbican to the south of the main castle. With 7,000 men Yukimura repelled Tokugawa assault after assault, launching three breakout attacks through the siege lines. The great generals of the shogun's army suffered embarrassing casualties against this one fortified outwork.

Ieyasu's generals could not break the castle by force. The siege settled into a stalemate. In December 1614 a negotiated truce was reached — and in that truce lay the real weapon. Ieyasu agreed to peace. Then, during the ceasefire, his engineers quietly filled in Osaka Castle's outer moats with soil. The castle's greatest defense was removed while its defenders believed the war was over.

The Summer Campaign of 1615 destroyed what the bell had supposedly insulted: the last Toyotomi. On May 8, 1615, Osaka Castle burned. Hideyori and Yodo-dono died inside it — most likely by suicide. The Toyotomi clan, which had unified Japan under the brilliant, mercurial 豊臣秀吉 (Toyotomi Hideyoshi), ceased to exist.

The bronze bell that began the war still hangs at Hoko-ji in Kyoto. It still bears the inscription that started nothing and ended everything.