The position of Emperor of Japan was, as I understand it, strictly hereditary, due to the necessity that the Emperor 'descend' from Amaterasu. Thus, the Shogun was not eligible to be Emperor, and despite his great military power would probably not have been accepted as such if he had simply declared himself Emperor.

However, couldn't he have done what Sejanus schemed to do as Tiberius' Praetorian Prefect? Apparently, his plan was to marry into the ruling Julio-Claudian family, not only to enhance his own status, but so that presumably one of his descendants might wear the Imperial Purple one day.

Why didn't the Shoguns try anything like this? Being Shogun is great, but being Emperor and the most powerful military force had to have been better. Was there something that prevented marriage into the Emperor's family?

  • 2
    In fact several historically powerful families did scheme to marry into the royal house. But it wouldn't have worked like you are thinking, because Emperors would not have doubled as Shoguns.
    – Semaphore
    Commented Nov 27, 2014 at 3:13
  • Well, I didn't mean the Emperor would have doubled as Shogun. I assume once the offices merged into one person, that person would simply have dropped the title 'Shogun' as superfluous. Commented Nov 27, 2014 at 3:16

3 Answers 3


There were several reasons why this could not or would not happen.

1. Shoguns were appointed officers of the state

Although one might describe the Shogunate as hereditary (in the same sense that the Crown of the Holy Roman Empire was "hereditary"), the office of Shogun was technically an Imperial appointment. Powerful samurai clans lobby the Imperial Court for appointment to this office, in order to legitimise their military governments with the backing of Japan's ancient civic laws. The heredity of their feudal power gave the impression of hereditary succession to their chosen titles[Note 1], but this is not strictly accurate.

This is more than just a matter of technicalities. The fact that the Shogun is not a feudal title, but rather an office of state, meant that a person would not "inherit" both positions. A reigning Emperor will not be appointing himself the new Shogun. It would be like HM Queen Elizabeth II asking herself to form a new government for the United Kingdom as her own Prime Minister. If ruling Shogun were to somehow ascend to the Chrysanthemum Throne, he wouldn't appoint himself his own Shogun.

In reality, when the Minamoto line of Shoguns went extinct, the Imperial Court appointed aristocrats and royals to head the Shogunate.

2. Neither Emperor nor Shogun would've run out of regular heirs

For one thing, they both typically had concubines for mass producing direct heirs.

More importantly, there was (and is) a long lasting, culturally acceptable tradition in Japan for adopting capable adults from other families as heirs - even after death. If a Shogun had no direct heirs, he most likely would have adopted someone. And if he died suddenly without making proper arrangements, his clan would find a nice puppet someone suitable for posthumous adoption. For example, when the Yonezawa lord Uesugi Tsunakatsu died without heir, his father-in-law arranged to have his dead body adopt his sister's son, two year old Kira Sannosuke, as the future Uesugi Tsunanori.

In any event, both the Imperial Family and most leading clans (including the Shoguns) typically have several branches, some explicitly for the purpose of providing backup heirs when the main line fails. For example, the Tokugawa Clan's senior (Shogunate) line went extinct on four occasions: The fourth, seventh, thirteenth and fourteenth shoguns all had no issue. In each case, the Shogunate Line was preserved via adoption from a cadet branch.

Similarly, the Imperial Family established several miyake, lit. Palatial Families', which were considered royal no matter how distant their relations to the reigning emperor gets. Their members were always eligible to inherit the throne, and did so on several occasions including the Go-Hanazono Emperor, who succeeded a third cousin. In effect, there was no single Imperial Family, but rather one crown bouncing between several Royal Families.

3. There would be absolutely no point to it.

Let's assume that the Shogun and Emperor really wanted to merge[Note 2], and did something crazy like adopt the Crown Price as his official heir.

As touched upon earlier, the office of Shogun did not confer power, but rather legitimised it. Thus, the real source of power was the hereditary feudal holdings of the samurai clans. The reason they became rulers of Japan was due to the political weakness and nonexistent military strength of the Imperial Court. If the Court remained weak, there was no conceivable way for it to maintain control over the Shogun's holdings. Thus, some other de facto governor must be appointed. He might not be called the Shogun, but there would have been no practical difference.

Alternatively, if the Court recovered its strength (which it started to do near the Meiji Restoration), then it could simply not appoint a Shogun - which, again, remained an imperial appointment right to the end. For example, the last Tokugawa Shogun, Yoshinobu, despite possessing (in theory) military superiority, broke upon being placed under Imperial Ban. He then fled from an impending battle with Imperial(-aligned) troops without a fight, and surrendered his lands, powers and titles to the Imperial Court.

4. Keeping the family name alive was a very important consideration

There isn't much to elaborate here. Japanese culture valued the continuation and perpetuation of the clan name. For example, a clan might expand its power by "inheriting" another domain (more of a Warring States era thing). This typically involves a junior son changing his name to the inherited clan's, rather than merge everything into the main title. The inherited clan thereafter became "part of the family", so to speak, despite the different surnames.

For example, the Mōri clan had the Two Mōri Kawas: the Kikkawa family and the Kobayakawa family. Both were renowned warrior families who were absorbed into the Mōri clan via being "inherited" by two junior sons of Mōri Motonari.

Note 1

There was no particular reason for the military governors of Japan to be styled Shogun. A sufficiently powerful and determined samurai lord can impress the Imperial Court into appointing himself Shogun (most popular), or Kampaku 関白 (chancellor-ish) (which Toyotomi Hideyoshi chose), or Sesshō 摂政 (regent) (like the Fujiwaras), or Daijō-daijin 太政大臣 (Prime Minister) (as Taira no Kiyomori achieved), or really anything they could think of or make up.

Note 2

In reality, the preferred historic method is to marry into the royal family while maintaining your own lineage of temporal power. The best example is the Fujiwara clan, who for centuries monopolised the powerful positions of Sesshō and Kampaku. They entrenched their position by marrying into the Imperial Family as Empress Consorts and Crown Princesses.

This was imitated by the early samurai regimes too. Taira no Kiyomori married his daughter Tokuko to the Takakura Emperor. Even Minamoto no Yoritomo, who overthrew the Taira regime and established the Kamakura Shogunate, attempted to have his daughters married into the Imperial Family - he was only thwarted because both daughters died young.

Later Samurai lords attempted similar tactics on occasion, though not to the same degree; for example, Shogun Tokugawa Ieyasu married his granddaughter Masako to Emperor Go-Mizunoō.

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    Fascinating answer. Commented Nov 27, 2014 at 7:23
  • but there is a point to it because during a point of civil chaos the emperor might legitimize someone else's claim to shogun The Battle of Toba Fushimi was a result of the Emperor wanting to seize power back. (as far as I know from TW) So ultimately the emperor is a potential threat in the future why not eliminate or put a family member on the throne?
    – Hao S
    Commented Jun 5, 2018 at 0:13
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    @HaoSun That's why they married into the imperial family so that the emperor is a son-in-law, or future nephew, or cousin.
    – Semaphore
    Commented Jun 5, 2018 at 1:25
  • so why wasn't Tokugawa able to do so and nullify the emperor for his heirs?
    – Hao S
    Commented Jun 6, 2018 at 4:21
  • @HaoSun You don't make any sense. Tokugawa Ieyasu married a granddaughter into the imperial family.
    – Semaphore
    Commented Jun 6, 2018 at 8:31

Actually, I believe you are mistaken in assuming that being the emperor meant having all of the power. In reality, during the periods from ~1200 to ~1870, the Shoguns were the ones who really had the military power and effectively controlled the country. The emperor was basically nothing more than a symbolic figurehead during much of this time.

The Kamakura shogunate (1192-1333) was the first of three major shogunates that controlled Japan during this time, and it was named for the city of Kamakura, which is where the Minamoto clan was headquartered. This shogunate controlled the military, administrative, and judicial functions, while the imperial government retained legal authority. This shogunate was formed by the Japanese warrior Yoritomo Minamoto, and his system of centralized feudalism would be the basic model on which future shogunates would build.

The second was the Ashikaga shogunate (1338-1573), which was established by Ashikaga Takauji and based in the imperial city of Kyoto. Much of this period was marked by civil wars where feudal barons (daimyo) and Buddhist monasteries built up local domains and private armies, which eventually led to the undermining of the Ashikaga shogunate.

The last of the three was the Tokugawa shogunate (1603-1867), which was formed by Tokugawa Ieyasu and headquartered in Edo (Tokyo). This shogunate was the most powerful of the three in that it controlled the emperor, the daimyo, and the religious establishments. In addition to this, they handled all Japanese foreign affairs.

Each of these shogunates represented a military dictatorship that essentially rendered the emperor ineffective, so there really never would have been any real desire for them to want to "wear the Imperial Purple". In spite of that, there were occasions where a shogun would actually choose a different member of the Imperial family to circumvent the line of succession, and Ieyasu even made his son the ruler in the place of the emperor.

  • I think you may have misunderstood my question. I never once suggested that being emperor meant having all the power. The office of Emperor was maintained during the Shogunates for a reason. While it had no temporal authority, it obviously had great symbolic power. So my question could be rephrased as, "Why would the Shogun not simply attempt to combine them?" Commented Nov 27, 2014 at 7:21
  • Ah, I see what may have tripped you up: "being Emperor and the most powerful military force". By "most powerful military force" I meant the Shogun, i.e., you could read this as "being Emperor and Shogun". Commented Nov 27, 2014 at 7:49

That's a bit like saying, why did no Prime Minister of England marry into the royal family to merge the two? It could happen of course, but it is not likely to, because of "jealousy" on both sides.

Let's look at the possible permutations as they may have occurred in Japan:

1) The Shogun, or one of his sons, marries the Emperor's oldest daughter. Women couldn't inherit the throne in Japan, so it would have gone to the Emperor's oldest natural son, or if necessary, the Emperor's oldest adopted son.

2) The Emperor or Crown Prince marries the Shogun's eldest daughter. That doesn't much work either. The Shogun is basically the country's chief warlord. Barring some once-per-millenninum exception (e.g. China's Wu Zhao or CiXi), women didn't make good warlords in the "old days."

3) The Emperor and Shogun "marry." Not possible before "modern" times, and its tolerance for same-sex marriages.

4) The Emperor adopts the Shogun as his son. That might actually be possible, but only if the Emperor had no other male heirs. The "ancients" were all conscious of their family lines, and most Emperors (and Shoguns) would shrink from "corrupting" theirs in this way.

It's true that the Minamoto Shogun line was a "branch" of the royal family. That would represent a de-merger of the two, which is a more logical result (given the laws of entropy). It's easier for a "distant" member of the royal family to "parachute" into the Shogunate, than it is for the Shogun to "rise" to Imperial Rank.

To use the English example, suppose Prince William eventually became King of England, while Prince Harry "resigned" from the Royal Family, ran for a seat in the House of Commons, and later became Prime Minister. That is a much more plausible scenario than some Prince Minister, call her Margaret, marrying Prince George in the royal family. (Most people become Prime Ministers at much older age than royal heirs to the throne marry.)

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    I think the rest of your points are solid, but 1) Go-Sakuramachi inherited the throne in 1762 from her brother, and 4) the Minamoto Shogunate line originated from the Imperial family. The Tokugawa did not, but also claimed descent from Minamoto. The name Minamoto itself was specifically chosen to mean "same origins".
    – Semaphore
    Commented Dec 15, 2014 at 18:29
  • @Semaphore: Added explanation.
    – Tom Au
    Commented Dec 15, 2014 at 20:12
  • 1
    I'm not sure how your edit addresses the point I made. Marrying back into your own ancestral family is not "corrupting", and women did ascend the throne.
    – Semaphore
    Commented Dec 15, 2014 at 20:50

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