The bell at Hōkō-ji temple in Kyoto is still there. A massive bronze bonsho (梵鐘), the deep-toned kind that Buddhist temples ring at dawn and dusk, hung between stone pillars in the temple grounds. The disputed characters are still legible in the metal, still exactly where they were when Tokugawa Ieyasu's advisors pointed at them and declared they concealed a curse.

The inscription reads: 国家安康、君臣豊楽 (kokka ankō, kunshin hōraku). "May the nation be peaceful and the house be safe; may lords and retainers rejoice in abundance." The monk Seikan Bun'ei of Nanzen-ji had composed it for Toyotomi Hideyori, who commissioned the bell as part of the reconstruction of the great Hōkō-ji temple his father had originally built.

Ieyasu's advisor Tenkai — a Buddhist monk then in his late seventies who had served Ieyasu for years and would eventually live to 107 — saw the problem immediately. Or presented one. The four-character phrase 国家安康 (kokka ankō) split Ieyasu's name: 家 (ie) and 康 (yasu) were separated by the character 安. In classical Chinese and Japanese usage, inserting characters into a name was considered to dismember it — a curse or omen of ill. Confucian scholar Hayashi Razan concurred. The second phrase, 君臣豊楽 (kunshin hōraku), also gave offense: the character 豊 (toyo) was the first character of the Toyotomi name, so the phrase read as wishing the Toyotomi — not their lords — glory and abundance.

Historians are nearly unanimous: this was a kōjitsu (口実) — a pretext, a manufactured grievance, a mouth-fruit offered as real justification for something that had already been decided. The four-character formulation 国家安康 is a completely standard classical Chinese phrase for "national peace and security." Seikan Bun'ei had likely not thought twice about it. It was the kind of text found in Buddhist inscriptions across East Asia.

But Ieyasu needed a reason. He had been watching Osaka Castle for fourteen years. Since Sekigahara in 1600, where he had broken the last organized opposition to Tokugawa rule, the Toyotomi had held on in their massive fortress on the edge of Osaka Bay. Hideyori was the son of Toyotomi Hideyoshi, the man who had unified Japan in the 1580s and whose legacy Ieyasu had carefully supplanted. Hideyori himself was not particularly threatening as a military commander, but he was a rallying point — a name, a claim, a castle that could attract any dissatisfied daimyo who wanted a flag to march under. As long as Hideyori lived and Osaka Castle stood, the Tokugawa succession was not truly secure.

Ieyasu was 71 years old in October 1614 — born January 31, 1543, he had passed his birthday that year. His health was beginning to deteriorate; he would die less than two years later, in June 1616, from what was likely stomach cancer or similar internal disease. He could not afford to leave Hideyori for his successor to deal with.

On October 11, Ieyasu departed Sunpu Castle and marched toward Kyoto, arriving at Nijo Castle on October 23. He did not dawdle. On October 25, he summoned two generals: Tōdō Takatora, a skilled castle engineer and field commander who had switched allegiance to the Tokugawa before Sekigahara, and Katagiri Katsumoto, one of Hideyoshi's famous "Seven Spears of Shizugatake" who had spent years serving as a liaison between the two houses.

Katagiri Katsumoto's appointment was darkly ironic. He had spent more than a decade trying to keep peace between the Tokugawa and the Toyotomi — a thankless position that required constant diplomacy with both sides. Eventually, Hideyori's mother Yodo-dono grew suspicious of his loyalty and had him expelled from Osaka Castle as a suspected Tokugawa spy. The expulsion destroyed the last political bridge between the two houses. The man sent to prevent war became, by his removal, one of its proximate causes. Now he was being ordered to lead the vanguard against the castle he had tried to protect through negotiation.

The force Ieyasu assembled was enormous: estimates range from 164,000 to 200,000 men. Hideyori's defenders numbered perhaps 100,000 — mostly rōnin, masterless samurai who had nowhere else to go and no better offer on the table. Active hostilities opened November 19, 1614, when Tokugawa troops crossed the Kizu River and destroyed a Toyotomi outpost.

The Winter Siege that followed ended in a ceasefire — and the ceasefire was a deception. One of the peace conditions required the outer moats of Osaka Castle to be filled in. Ieyasu's men filled not only the outer moat but the inner ones as well, stripping the fortress of its greatest defensive advantage. The Summer Campaign in 1615 lasted only days. Osaka Castle fell and burned. Hideyori and his mother Yodo-dono died inside — along with Hideyori's infant son. The Toyotomi clan was extinct.

Katagiri Katsumoto died June 24, 1615, twenty days after the castle fell, from causes that were never officially recorded. Tōdō Takatora survived and prospered, going on to fight at the Battle of Yao in the Summer Campaign and remaining a valued Tokugawa general until his death in 1630.

Ieyasu himself died June 1, 1616. He had achieved his last objective with almost nothing to spare.

The bell at Hōkō-ji is still there. The inscription is still legible. Four characters that gave a 71-year-old man who needed one reason just enough.