How Oda Nobunaga Won at Okehazama: The Formula Behind the Impossible Victory

"Charge!, Attack!"
Noon, May 19, 1560 (Eiroku 3). At the moment when the torrential rain and rolling thunder that had poured down over the Okehazama area began to fade—“Now is the time! Attack! Kakare~!”

Under Oda Nobunaga's (1534-1582, 織田信長) order for an all-out assault, only 2,000 elite troops charged straight toward the headquarters of Imagawa Yoshimoto (1519-1560, 今川義元). Amid chaos, Yoshimoto, renowned as the greatest archer of the Tokaido region and a prominent feudal lord, was steadily pushed back by Nobunaga's elite troops attacking one after another and was finally killed at Dengakutsubo, around present-day Okehazama Battlefield Park. The end of this powerful feudal lord, who had led an army of 25,000 men, came in only a matter of hours.

This single battle dramatically reshaped the political landscape of Japan’s Warring States (1467–1590) period and became the turning point from which Nobunaga would rise toward the unification of the country.

Two Days Leading Up to the Battle

The story goes back to the day before.
On May 18, the eve of the battle, Matsudaira Motoyasu (1543-1616, later Tokugawa Ieyasu, 徳川家康), serving under Imagawa, succeeded in delivering army provisions into Odaka Castle. Early in the morning of the following day, the 19th, Motoyasu's force and another force launched attacks on Oda's Marune and Washizu fortresses surrounding Odaka Castle, causing both fortresses to fall around 10:00 a.m.
Receiving this urgent report at Kiyosu Castle, Nobunaga performed Atsumori, a famous piece of the Kowaka Mai dance-drama tradition.

“The 50 years of the human realm, one of 6 realms of Buddhism, it’s too short to live”

Nobunaga’s Kowaka Mai may have been a dance to mark his determination to fight against Imagawa Yoshimoto, one of the greatest feudal lords of the Warring States period. And the die was cast. After finishing the dance, Nobunaga departed Kiyosu Castle with only six cavalrymen.

Around 8:00 a.m., after praying for victory at Atsuta Shrine, he hurried directly to Zenshoji Fortress. At the fortress, approximately 3,000 troops were already waiting for him, following Nobunaga’s orders issued the previous night. Around 10:00 a.m., Nobunaga had numerous streamers set up at Zenshoji Fortress and ordered a 300-man ranger force to attack Imagawa’s vanguard force. Nobunaga himself led approximately 2,000 elite troops, crossed the Ougi River, and entered Nakajima Fortress. From there, to avoid detection by Imagawa scouts stationed at Takaneyama, Makuyama, and Makiyama mountains, his troops continued along the Ougi River and advanced along the foot of the mountains, drawing closer to a grove near Yoshimoto’s headquarters.

Around 11:00 a.m., Yoshimoto’s main camp was filled with celebration at the news that the two fortresses had fallen. Encouraged by the victory, Yoshimoto sang in high spirits—

and at that very moment, a violent thunderstorm struck the entire Okehazama area. The Imagawa soldiers removed their helmets and armor and took shelter in the wooded area to avoid lightning strikes.

And then came that famous command—the instant the rain stopped.

Why Is Nobunaga Driven into Such Dire Circumstances?

But why had Nobunaga been pushed into such a desperate situation in the first place? The story goes back eight years.

In March 1552 (Tenbun 21), at his father's funeral, Nobunaga appeared before the Buddhist altar without wearing a hakama and with his hair tied in a Chasen-mage style (resembling a tea whisk). He grabbed a handful of incense powder and threw it on his father's tablet. This act, reflective of Nobunaga's unconventional demeanor, caused the loss of centripetal force within the Oda family, leading to division. At that time, Nobunaga controlled no more than one-third of Owari Province.

Internal crises struck one after another: the attack by the lord of Kiyosu Castle (August 1552), the betrayal of the lord of Kasadera Castle, the defection of the lords of Narumi, Odaka, and Kutsukake Castles to the Imagawa clan (1553), the rebellion of his half-brother, lord of Moriyama Castle (1555), the rebellion of his younger brother (May 1556), and the movement by the lord of Iwakura Castle—the head family of the Oda clan—to overthrow Nobunaga (July 1558).

Outside, there stood Imagawa.

Yoshimoto steadily dismantled Oda’s positions. He occupied Shigehara Castle on the Oda side and built Muraki Fortress (1554) to divide Ogawa Castle and Chita Castle on the Oda side. Nobunaga fought a series of some 40 battles under harsh conditions.

Despite these challenges, Nobunaga managed to quell rebellions, employing firearms for the first time at the Battle of Muraki Fortress, which fell under his control. Then, he built fortifications surrounding Narumi Castle and Odaka Castle, which had been previously turned over to the Imagawa, in preparation for the coming battle.

Given the longstanding conflict with the Imagawa clan dating back to his father’s generation, a direct clash had become unavoidable. And then, in March 1560 (Eiroku 3), Yoshimoto finally departed Sunpu with a formidable force of 25,000 soldiers and began his invasion of Owari.

And Then Came Tenka Fubu

Following the victory at Okehazama, Nobunaga’s momentum accelerated. Seven years later, in 1567 (Eiroku 10), upon entering Gifu Castle, Nobunaga made a bold declaration: Tenka Fubu.

At a time when the feudal lords of the Warring States period continued to fight merely to expand their territories, Nobunaga distinguished himself by clearly presenting a broader vision:

to bring peace and order to the realm centered on Kyoto, where the Ashikaga shoguns, the Emperor, and the court nobility resided.

He became the first Sengoku daimyo to articulate such an ideal so explicitly. To symbolize this vision, Nobunaga began using the red seal of Tenka Fubu on his official letters.

What was the reason for the victory of Oda Nobunaga with 3,000 troops over Imagawa Yoshimoto, who led 25,000 soldiers and had ties to the Ashikaga shoguns of the Muromachi shogunate? Although there are several theories, one formula for victory is presented here.

Then Why Does Nobunaga Win?

3,000 against 25,000.
By conventional wisdom, victory should have been impossible. Moreover, the victory at Okehazama was neither the often-told story of a “fortunate thunderstorm” nor a mere “lucky surprise attack.” Behind it lay a carefully constructed formula for victory built by Nobunaga.

In fact, there is a strong possibility that the number of troops actually defending Yoshimoto’s headquarters was fewer than 2,000. Why was Yoshimoto—who had commanded a force of 25,000—protected by only a force nearly equal in number to Nobunaga’s?

What did Nobunaga know?
What did he foresee?
And what did he set in motion?

The Formula for Nobunaga’s Victory

Although there are several theories, one interpretation may be summarized into a single formula. The key was this:

Disperse Yoshimoto’s 25,000 troops, reduce the number of soldiers defending his headquarters to the limit, and strike at Yoshimoto alone.

Dispersing the Forces

Of the estimated 5,000 to 6,000 soldiers assigned to guard Imagawa’s headquarters, many served non-combat roles—carrying Yoshimoto’s palanquin, preparing meals, and supporting camp operations. According to Professor Emeritus Owada Tetsuo of Shizuoka University, the number of actual combat-ready troops may have been fewer than 2,000. Against them stood Nobunaga’s elite force of approximately 2,000 men.

At the decisive moment, the two sides were nearly equal in effective strength. In other words, it was not that the outnumbered Nobunaga created a miracle—it was that by turning the battle into an even contest, half the victory had already been secured.

But how did Nobunaga reduce the number defending Yoshimoto’s headquarters?

Three Tactics

Tactics 1— Pin Down the Front Line
On the morning of the 19th, Nobunaga deliberately chose not to send reinforcements to the Marune and Washizu Fortresses. If troops had been diverted to rescue the fortresses, the main force would have weakened. Prepared to sacrifice the forts if necessary, Nobunaga pinned down Ieyasu's and Asahina's forward units and prevented them from joining Yoshimoto's headquarters.

Tactics 2— Create the Illusion of Presence
Nobunaga deployed numerous streamers at Zenshoji Fortress to make it appear as though his main army remained there. This deception drew the attention of the Imagawa forces and delayed their reaction.

Tactics 3— Scatter the Bait
Nobunaga ordered approximately 300 troops to attack Imagawa's vanguard force. This maneuver pulled several hundred additional soldiers away from Yoshimoto's headquarters. Each move by itself was small. But together, they steadily weakened the defense around Yoshimoto.

The Decision to Raid the Main Camp — and Absolute Secrecy

One factor that should not be overlooked was Nobunaga’s political situation. Although he had begun to stabilize Owari, he still did not know who might betray him next. For that reason, Nobunaga feared leaks of information. On the night before the decisive battle, Nobunaga gathered his retainers at Kiyosu Castle, but held no war council. Instead, he spent the evening in ordinary conversation and dismissed them.

At the night deepened, it is said that the retainers muttered:

“Now the Oda family will surely be destroyed."

The defensive strategy proposed by his retainers assumed reinforcements would arrive. But Nobunaga had no such rear guard to rely upon. The only person he could once depend upon—his father-in-law, Saito Dosan—had already passed away.

Intelligence Capability

What supported Nobunaga’s decision was his extraordinary ability to gather information.

Two days before the battle, Nobunaga received word that Sena Ujitoshi of the Imagawa forces had prepared ground for Yoshimoto’s headquarters around Okehazama Hill with approximately 200 soldiers. From this, Nobunaga became convinced:

Yoshimoto’s headquarters could only be here—at Okehazama.

It was the only location capable of providing water for soldiers and approximately one hundred horses. For Nobunaga, the hills and valleys of Okehazama were familiar ground. Since his youth, he had run through these fields with his attendants and likely knew every road, mountain, and river. As long as Yoshimoto entered Okehazama, Nobunaga must have believed victory was possible.

Then came another crucial report. Yoshimoto had departed Kutsukake Castle not on horseback, but in a palanquin. This changed everything.

At the time, none of Nobunaga’s soldiers knew what Yoshimoto looked like. But with a clear order—

“Aim for the palanquin.”

—the entire force could focus on a single target.

Yanada Masatsuna, who delivered this intelligence, was later praised as the greatest contributor after the battle. It was proof of how highly Nobunaga valued information.

If Taigen Sessai Has Still Been Alive

There is another circumstance that cannot be overlooked.

For Yoshimoto, Okehazama was the first campaign he personally commanded after the death of his military advisor, Taigen Sessai. Sessai had been an exceptional strategist who supported Yoshimoto throughout his rise. Meanwhile, Nobunaga had spent his days pursuing the unification of Owari through battles and political maneuvering. He possessed strategies and tactics refined through real combat, practical experience, and the determination expected of the ruler of Owari.

The difference in battlefield experience and local familiarity may have greatly shaped the outcome. History has no “if.” And yet one cannot help but wonder— What if Sessai had still been alive?

Blessings of the Atsuta Deity

The Shinchoko-ki (The Biography of Nobunaga) records:

“Suddenly heavy rain and hail struck the faces of the enemy… people said perhaps it was the divine army of Atsuta Daimyojin.”

After the victory, Nobunaga dedicated an earth wall approximately 400 meters in length—later known as the Nobunaga Wall—to Atsuta Jingu Shrine. To Nobunaga as well, the thunderstorm that came at precisely the right moment must have appeared as divine favor.

At Kiyosu Castle, Nobunaga identified Yoshimoto’s head and conducted memorial services by reciting the Senbukyo sutra. Afterward, Yoshimoto’s head was returned to Sunpu.

Yoshimoto's Samonji - A Sword That Carries the Legacy of Two Warlords

Yoshimoto's favorite sword, Yoshimoto-samonji, which he wielded during his battle against Nobunaga’s troops at Okehazama, later passed into Nobunaga's hands. Nobunaga treasured the sword and had gold inlay engraved:

On the front:

“The sword carried when Yoshimoto was captured on May 19, Eiroku 3”

And on the reverse:

“Oda Nobunaga, Governor of Owari”

The sword would later pass through the hands of Tototomi Hideyoshi, Tokugawa Ieyasu, and successive Tokugawa shoguns. In 1878 (Meiji 11), it was dedicated to Kenkun Shrine in Kyoto, which enshrines Nobunaga's spirit. Today, it remains an Important Cultural Property that continues to tell the story of two extraordinary leaders.

Visit Okehazama Battlefield Park and experience for yourself the atmosphere of the place where these two great commanders once collided.

Interviewed Kajino Yukio (Auditor and Director of the Guide at The NPO, Okehazama Battlefield Preservation Society)

The Battle of Okehazama Timeline

		Oda Nobnaga	Imagawa Yoshimoto
1560/5/12			Left Sunpu for Owari
1560/5/18	Evening	A meeting at Kiyosu Castle but no military discussions	Arrived at Kutsukake Castle
	Night	Received two pieces of information - Yoshimoto's main camp at Okehazama - Yoshimoto will attack Marune & Washizu Fortress on May 19 morning	Brought army provisions into Odaka Castle
1560/5/19	Early morning	Received the beginning of Yoshimoto's attack on Marune & Washizu Fortress	Yoshimoto's forces started to attack on Marune & Washizu Fortress
		Danced “Atsumori” at Kiyosu Castle
		Get out from Kiyosu Castle with only six cavalrymen
	8am	Prayed for victory at Atsuta Shrine
	10am	Arrived at Zenshoji Fortress and had a streamer set up	Heard the fall of Marune & Washizu Fortress
		Ordered a 300-man ranger force to attack Yoshimoto's vanguard force.
	11am	Crrosed the Ougi River and entered Nakajima Fortress	Sang a song in high spirits upon the fall of the two fortresses
		Proceeded along the mountain bank along the Ougi River toward Okehazama	Took a short rest at Okehazama
		A heavy thunderstorm mixed with hail was brewing
	Noon	Ordered to the fierce charge on Yoshimoto's headquarters	Was finally killed at Dengakutsubo

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