A regent (Sessho), in a state with a monarchy, is the practice of carrying out government and national affairs in place of the monarch, or the post that does so, when the monarch is unable to do so because he is an infant, ill or not in the country. In many cases, the post is filled by the monarch's successor (e.g. a prince), brother, mother, or a maternal relative such as a grandfather or uncle on the mother's side.
The Early Modern Period
Regarding the period in which Empress Jingu governed, "Chronicles of Japan" made a 'Record of the Regent Empress Jingu,' who is seen as Japanese history's first regent, but this is an imposition of later concepts onto the past, and does not leave the realm of legend. Generally, in Japanese history a regent is defined as the practice of receiving an imperial edict and conducting government in place of the emperor or one who does so, and it is generally accepted that the historical first regent was Prince Shotoku at the time of Empress Suiko.
Later several members of the imperial family became regents, but under Risturyo the post in charge of the regency was not defined. However, since FUJIWARA no Yoshifusa became the first outside of the imperial family to be regent in 866, a regent was appointed for an infant emperor, and a Kanpaku (chief adviser to the Emperor) once he was an adult, after which many members of the emperor's extended family in the Fujiwara clan (the Northern House of the Fujiwara clan) became regent and Kanpaku.
At this point, the regent, as the post of one who conducted government in the emperor's place, came to be defined as an official outside of Ritsuryo. While the regent carried out (as an agent) government in the place of an infant emperor, he also at that time oversaw the emperor's major power to manage officials and took charge of appointments and promotion of officials.
Although under the Fujiwara clan the regent came to be thought of as a bureaucratic post to be held concurrently by a minister, which was an official post, in 986 at the time of FUJIWARA no Kaneie, he quit his position as Udaijin (Minister of the Right), which was an official post (Shokujikan), to become only a regent with an official rank but no post (Sankan). At that time, the Myobo and Myogyo Kanmons (reports) were issued regarding the status of the regent. In the former, (1) three high level bureaucrats (Grand minister of state and Ministers of the Right and Left) were heads of the Grand Council of State, but the regent did not have an official rank. (2) Under the Ritsuryo system, the rank of bureaucrats was dependent upon their post, and although as a rule First Order was the top, because Shokujikan preceded sankan (a position without specific roles), a First Order Sankan was after Chunagon (vice-councilor of state), and before Sangi (councillor). (3) However, Kaneie was already treated as a Jusangu (honorary rank next to the three Empresses: Great Empress Dowager, Empress Dowager, and Empress), which exceeded the three high level bureaucrats, and was allowed to sit in a higher position than them. Even without that, the appointment to regent decreed 'service in state affairs,' so if that treatment was laid out in an imperial decree, it was so. In the latter, it was argued that the regent was of a different nature than the three high level bureaucrats and should not be considered equivalent to general court nobles (consequently, in the palace he should be in a higher position than the three high level bureaucrats).
From around the time of the 11th century FUJIWARA no Michinaga, except for the period of the Kenmu Restoration, it became a permanent post. Later, the descendants of FUJIWARA no Michinaga came to be either regent or Kanpaku at all times, regardless of their family relationship.
After the Kamakura period, the Northern House of the Fujiwara clan split into Gosekke (the five families of the Fujiwara clan whose members were eligible for the positions of Sessho and Kanpaku), Konoe, Ichijo, Takatsukasa, Kujo, and Nijo families, and whoever among them held the highest official rank was appointed regent/Kanpaku, a situation which continued until the Meiji Restoration. The two exceptions to this are Hideyoshi TOYOTOMI and Hidetsugu TOYOTOMI.
Prior to the Meiji Restoration the regents carried out most of the emperor's governmental affairs, such as writing imperial edicts, conferring ranks and making appointments, and their power was nearly the same as that of the emperor.
The Later Modern Period
In 1889, based on the Imperial Constitution and Former Imperial House Act, a system was laid out to put an imperial regent in the emperor's place when the emperor had not reached the age of maturity or could not wield sovereign power. The regent had almost the same authority as the emperor, but did not have authority to amend the constitution or to expand (amend) the Imperial Household Law. From Emperor Taisho's last years in 1921 to his death in 1926, Crown Prince Hirohito (later Emperor Showa) served as regent. During that period, Crown Prince Hirohito is also known as Sessho no Miya.
A regent system was also created by the Constitution of Japan and Imperial Household Act enacted in 1947. As specified in the Constitution of Japan, the regent is a position to carry out national affairs in the name of the emperor, and has exactly the same authority as the emperor regarding national affairs. When the emperor has not yet reached the age of maturity, or due to a serious illness or accident is unable to conduct national affairs, a regent will be placed at the discretion of the Imperial Household Council.
The temporary agent for national affairs is given as an example of something similar to a regent. In the event of the emperor's disease or accident, such as hospitalizations or trips abroad, based on appointment (transmission of chokusho, official document issued by Emperor, to a temporary agent for national affairs) by the emperor at the advice and approval of the cabinet, national affairs are temporarily carried out by an agent. This is a system that was put in place so that national affairs could be entrusted to someone in the event of the emperor's illness or accident, without going so far as appointing a regent.
Under the Japanese Constitution, there has so far been no example of a regent being appointed.
Succession to regent and temporary agent for national affairs proceeds in the following order of adult members of the imperial family.
Crown Prince, Emperor's Grandson
Imperial Princes and Males of the Imperial Family
Grand Empress Dowager
Imperial Princesses and Females of the Imperial Family
The fact that women can take the position is different from imperial succession. However, regarding an Empress, Empress Dowager, or Grand Empress Dowager, the possibility of person of common birth entering a regent position as the emperor's agent and conducting national affairs has never been discussed; and some worry about the possibility that in the future if such a situation arose, it would develop into a very difficult problem. As a solution to such a situation, one view is that birth in the royal family should be made a condition for an Empress, Empress Dowager, or Grand Empress Dowager to become regent.
In China, in the event that the emperor was unable to perform his duties, there were instances of the imperial family supervising government as national directors. Mostly a prince would be the national director, but in the Qing Dynasty there were cases of the emperor's uncle (Dorgon) or father (Zaifeng) conducting government as regent of national director. Also in the various historical dynasties there were instances of an Empress Dowager conducting governance by women.
In the Byzantine Empire, there were instances of the Archbishop of Constantinople, who was the head cleric, filling the post of regent. Also, as with Horthy Miklos in the kingdom of Hungary between wars, sometimes there was only a regent because the monarch was absent.