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Why Did Akechi Mitsuhide Betray Him? A Fair Breakdown of 5 Theories on the Honno-ji Incident

2026年7月19日 20:45

Early morning, June 2, 1582, at Honno-ji Temple in Kyoto.

Surrounding his lord, Oda Nobunaga, was the army of Akechi Mitsuhide, who should have been his ally. When Nobunaga asked who was rebelling, his page, Mori Ranmaru, replied, "It appears to be Akechi's forces." It is said that upon hearing this, Nobunaga muttered, "It cannot be helped."

This is a scene many have likely seen in historical dramas or programs. Why was a man on the verge of unifying the country struck down by the vassal he should have trusted most? And why did Mitsuhide turn his blade against his lord?

In fact, the reason remains unresolved to this day.

It may come as a surprise, but the true motive behind Mitsuhide's attack on Nobunaga remains unclear, even after decades of professional historians examining the historical records.

"If there is no answer, is there any point in reading about it?"

Did you feel that way? However, I believe that is precisely why it is interesting. The fact that there is no settled answer means that each of us can construct our own reasoning from the fragments of historical records.

In this article, I have fairly organized the five major theories that have been discussed as Mitsuhide's motives, presenting the "strengths" and "weaknesses" of each without declaring any one of them the definitive answer.

What you will learn in this article

You can quickly organize the framework of what happened during the Honno-ji Incident.
You can understand the five theories regarding his motives, along with their respective strengths and weaknesses.
You will learn how far historical research has come (including recent prominent theories).
You will gain a perspective that allows you to say, "I support this theory," the next time you watch a historical program.

"Resentment," "Ambition," "Shikoku," "Fear," and "The Mastermind." Even if you have heard the names, perhaps few people have organized the details and weaknesses of each.

Please take your time to savor one of the greatest mysteries in Japanese history, which has remained unsolved for over 400 years. By the time you finish reading, you might have formed your own "personal theory."

Introduction

In this article, we will organize the five major theories surrounding Akechi Mitsuhide's motives for the "Honno-ji Incident," often called the greatest mystery in Japanese history, by presenting the strengths and weaknesses of each. By the time you finish reading, you may be able to hold your own view, saying, "This theory makes the most sense to me."

1. Conclusion: The truth remains unknown even now

First, I will tell you the most important thing. The true reason why Mitsuhide struck down Nobunaga remains unresolved to this day.

"So, there is no answer?" you might be disappointed. However, I believe this is where the interest lies. Even after decades of professional historians facing the historical records, no definitive evidence has been found. That is precisely why there is room left for each of us to construct our own reasoning from the fragments of historical records.

This article does not aim to impose a single 'correct' answer. Instead, it presents the major theories fairly, aiming to provide you with the materials to form your own conclusions.

2. What Happened at Honno-ji That Day

First, let's briefly review the framework of the incident.

Early on the morning of June 2, Tensho 10 (June 21, 1582). Akechi Mitsuhide's army, which was supposed to be departing to support the campaign against the Mori clan in the Chugoku region, changed its course and attacked their lord, Oda Nobunaga, who was staying at Honno-ji Temple in Kyoto.

While Nobunaga had only a small retinue with him, it is said that Mitsuhide's army numbered over 10,000. Upon noticing the disturbance, Nobunaga asked who was rebelling, and his page, Mori Ranmaru, is said to have replied, 'It appears to be the Akechi army.' The anecdote that Nobunaga, upon hearing this, muttered 'zehi ni oyobazu'—meaning 'it cannot be helped'—is very famous. It is said that Nobunaga set fire to the temple and took his own life.

Furthermore, his eldest son, Nobutada, who was at a nearby location, was also surrounded by Mitsuhide's forces and committed suicide after moving to the Nijo Shin-gosho to resist. In fact, this Nobutada had been granted the headship of the family by Nobunaga in Tensho 3 (1575), so the official head of the Oda family at this time was already Nobutada. The reality seems to be that while Nobunaga was technically retired, he continued to hold actual power. In other words, in this single day, both the former head who held the real power and the head who had inherited the family name were lost simultaneously. Try to imagine just how massive a blow this was to the Oda family.

By the way, it has been pointed out that the phrase widely known as Mitsuhide's words, 'The enemy is at Honno-ji,' may be a story created by later generations. It is said that it does not appear in primary historical sources from the time, and may have become established as it was retold as a dramatic scene. Historical anecdotes are filled with many such 'well-crafted stories that may or may not be true.' Perhaps enjoying history involves savoring those elements as well.

3. Five Theories Regarding the Motive

This is the main subject. I will present five representative theories that have been discussed as Mitsuhide's motives. Let's look at the 'strengths' and 'weaknesses' of each.

① The Resentment Theory
This is the oldest and most widely known theory. It is the view that resentment built up due to repeated reprimands and humiliations received from Nobunaga. Anecdotes are also passed down, such as one where Mitsuhide, tasked with entertaining Tokugawa Ieyasu, was publicly scolded by Nobunaga over his handling of the event.

Strength: It is easy to understand as a motive, feels human, and is easy to empathize with as a story.
Weakness: It is pointed out that the episodes of resentment often involve later embellishments or fabrications, and lack strong support from historical sources. Many of these stories seem to have been inflated in literature from the Edo period.

② The Ambition (Seizing the Realm) Theory
This is the theory that in an era where the spirit of 'gekokujo' (the low overcoming the high) remained, Mitsuhide himself aimed to rule the country.

Strength: Indeed, after the incident, Mitsuhide showed moves to seize power, such as by approaching the Imperial Court.
Weakness: There is little evidence of careful prior preparation, and it looks like it was a gamble with little prospect of success.

③ The Shikoku Theory
This is a theory that has received particular attention in recent years. Nobunaga initially had a policy of leaving Shikoku to Chosokabe Motochika, but he changed this. This view holds that Mitsuhide, who had been acting as the negotiator with Motochika, lost face and was driven into a corner. It is also said that the scheduled departure date for the Shikoku conquest army was June 2, the same day as the incident, and some researchers place great importance on this coincidence.

Strength: It is considered persuasive because it is based on specific political circumstances rather than personal emotions. The discovery of related letters in recent years is also said to support this theory.
Weakness: The question remains whether that alone would be enough of a motive to kill one's lord.

④ The Fear (Self-Preservation) Theory
This is the theory that the action was taken out of fear that he would eventually be purged himself if things continued as they were.

Strength: Nobunaga had already exiled senior retainers like Sakuma Nobumori, so it is not unnatural for Mitsuhide to have felt anxious about his future.
Weakness: If he was afraid, it is difficult to explain why he chose the most dangerous path of rebellion.

5. The Mastermind Theory
This theory suggests that someone was pulling the strings behind Mitsuhide. Various names have been suggested, including the Imperial Court, Shogun Ashikaga Yoshiaki, Hashiba Hideyoshi, Tokugawa Ieyasu, and even the Jesuits.

Strength: It has narrative appeal, and what appear to be circumstantial evidence are often cited.
Weakness: None of these have a decisive factor, and no definitive historical evidence has been found.

4. How far has recent research come?

So, what is the current view among experts?

The general trend seems to be shifting away from grand conspiracy theories involving masterminds toward focusing on the political situation Mitsuhide personally faced. In particular, the Shikoku theory is said to be gaining support due to its high level of specificity.

Furthermore, the "multiple factors theory" has become prominent in recent years. This is the idea that rather than explaining it with a single reason, multiple elements—such as resentment, anxiety, political deadlock, and the arrival of a golden opportunity—overlapped and converged at that very moment. When people make major decisions, it is perhaps rare for there to be only one reason.

Moreover, the existence of an "opportunity" cannot be overlooked. On that day, Nobunaga was on the verge of unifying the country, yet he had only a small escort with him in Kyoto. Mitsuhide had his own large army nearby. No matter how much motivation one might have, a rebellion cannot occur unless the circumstances are right. Perhaps it was the coincidence of motivation and opportunity intersecting at the same point that moved history.

5. Looking at Mitsuhide as someone who worked in an organization for a long time

I would like to change our perspective a little here.

I think the Shikoku theory and the fear theory suddenly become very vivid when you look at Mitsuhide not as a "Sengoku warlord," but as "a person who has worked in an organization for a long time."

First, how old was Mitsuhide? Actually, it is not clear. There is no record of his birth year in reliable contemporary historical documents, and later records suggest he was 54, 66, or even 69 years old. While there is a range, he was certainly not a novice.It is highly likely that he was at an age approaching the end of his career. possibilities.

Let's translate the situation Mitsuhide was in into modern terms.

Negotiations with Shikoku, which he had been in charge of for a long time, were scrapped due to a change in policy from above (Shikoku theory).
A senior colleague he had served for many years was exiled because he had not produced results (fear theory).

The latter refers to Sakuma Nobumori. He was expelled from the Oda clan after being presented with a letter stating that he had failed to achieve results despite being stationed at the Ishiyama Hongan-ji war for five years. This happened in 1580, just two years before the Honno-ji Incident. He went to Mount Koya and passed away there.

The work you have been responsible for for a long time disappears due to a single decision from above. A senior colleague who has contributed for a long time leaves, being told they lack sufficient achievements. And you yourself are approaching the same age as that senior colleague.

—Is this a story that only happened 400 years ago?

Mandatory retirement, reassignment, business restructuring. I suspect there are many people who have seen similar things happen, even if the names are different. How has it been in your workplace?

Of course, this is not to say that Mitsuhide's actions were correct. Treason is treason. However, the feelings of "losing face" or "I might be next" are something I feel I can understand, regardless of the era.

Thinking about it this way, perhaps our choice of theory reveals something about ourselves. If I had read these five theories in my twenties, I probably would have chosen the grudge theory or the mastermind theory. Because they are interesting as stories. That is not the case now.

I cast my vote for the multi-factor theory. Resentment, anxiety, and being at a dead end—none of these are enough on their own. But when they pile up, a perfect opportunity just happens to arise. Isn't that usually how it goes when people make major decisions?

6. Which theory do you believe in?

I have laid out five theories, but what did you think?

Those who empathize with the human element of the grudge theory
Those who are convinced by the specificity of the Shikoku theory
Those who feel the multi-factor theory is the most realistic

Every perspective has points that make you nod and points that make you hesitate. And as of now, there is no "correct answer" to finally judge them.

Perhaps that is why this mystery has continued to fascinate people for over 400 years. The next time you see the Honno-ji Incident in a historical drama or program, please try watching it with your own theory in mind. You will surely see a different landscape than before.

If you'd like, please share your vote in the comments. "I'm for the Shikoku theory," or "No, it has to be the grudge theory"—I would be even happier if you included your reasons. I believe the fascination of this incident lies in the fact that people choose different theories even when looking at the same historical materials.