Japanese political concept
 is a concept in the Japanese language translatable as "system of government", "sovereignty", "national identity, essence and character", "national polity; body politic; national entity; basis for the Emperor's sovereignty; Japanese constitution" or nation.
Etymology.
"Kokutai" originated as a Sino-Japanese loanword from Chinese "guoti" (; "state political system; national governmental structure"). The Japanese compound word joins and . According to the "Hanyu Da Cidian", the oldest "guoti" usages are in two Chinese classic texts. The 2nd century BC "Guliang zhuan" () to the Spring and Autumn Annals glosses "dafu" () as "guoti" metaphorically meaning "embodiment of the country". The 1st century AD "Book of Han" history of Emperor Cheng of Han used "guoti" to mean "laws and governance" of Confucianist officials.
Before 1868.
The historical origins of "kokutai" go back to pre-1868 periods, especially the Edo period ruled by the Tokugawa shogunate (1603–1868).
Aizawa Seishisai (会沢正志斎, 1782–1863) was an authority on Neo-Confucianism and leader of the Mitogaku (水戸学 "Mito School") that supported direct restoration of the Imperial House of Japan. He popularized the word "kokutai" in his 1825 "Shinron" (新論 "New Theses"), which also introduced the term "Sonnō jōi" ("revere the Emperor, expel the barbarians").
Aizawa developed his ideas of "kokutai" using the idea that the Japanese national myths in the "Kojiki" and "Nihon Shoki" were historical facts, believing that the Emperor was directly descended from the sun goddess Amaterasu-ōmikami. Aizawa idealized this divinely-ruled ancient Japan as a form of "saisei itchi" (祭政一致 "unity of religion and government") or theocracy. For early Japanese Neo-Confucian scholars, linguist Roy Andrew Miller says, ""kokutai" meant something still rather vague and ill defined. It was more or less the Japanese 'nation's body' or 'national structure'."
From 1868 to 1945.
From 1868 to 1890.
Katō Hiroyuki (1836–1916) and Fukuzawa Yukichi (1835–1901) were Meiji period scholars who analyzed the dominance of Western civilization and urged progress for the Japanese nation.
In 1874, Katō wrote the "Kokutai Shinron" (国体新論 "New Theory of the National Body/Structure"), which criticized traditional Chinese and Japanese theories of government and, adopting Western theories of natural rights, proposed a constitutional monarchy for Japan. He contrasted between "kokutai" and "seitai" (政体 "government body/structure"). Brownlee explains.
 ;templatestyles src="Template:Blockquote/styles.css" / ;The "Kokutai-seitai" distinction enabled conservatives to identify clearly as "Kokutai", National Essence, the "native Japanese", eternal, and immutable aspects of their polity, derived from history, tradition, and custom, and focused on the Emperor. The form of government, "Seitai", a secondary concept, then consisted of the historical arrangements for the exercise of political authority. "Seitai", the form of government, was historically contingent and changed through time. Japan had experienced in succession direct rule by the Emperors in ancient times, then the rule of the Fujiwara Regents, then seven hundred years of rule by "shōguns", followed by the allegedly direct rule of the Emperors again after the Meiji Restoration. Each was a "seitai", a form of government. In this understanding, the modern system of government under the Meiji Constitution, derived this time from foreign sources, was nothing more than another form of Japanese government, a new "seitai". The Constitution was nothing fundamental. The concept of the "kokutai" was popularized during the Meiji era as Japanese elites had embraced a "crude Social Darwinism" as their guiding principles, seeing nations as being locked in perpetual struggle with one another for dominance, and as such the purpose of the Japanese state was first and foremost as a machine for conducting foreign policy. In order to maintain support for the existing social system and for this view as the state for a machine for conducting foreign policy, the idea of the "kokutai" was popularized with the Japanese people being liked to one vast family under the rule of the patriarchal god-emperor. The American historian M. G. Sheftall wrote that the concept of the "kokutai" was the ideological foundation stone of Japanese militarism, writing for millions of Japanese the "kokutai" was "...the mystical embodiment of the essential unity of the Japanese people, inextricably bound up with "völkish" ideas about the mythical divine origins of the nation, all under the august beneficence of the institution of the divine emperor and the proverbial protection of several millennia worth of ancestral ghosts. For the IJA [Imperial Japanese Army] and tens of millions of Emperor Meiji's subjects, the "kokutai" was not merely a source of pride and spiritual power for the nation, it was the lifeworld of the nation "in toto", not only in social and political terms, but also in theological and cosmological terms, and no means were too extreme and no sacrifice too great if deemed necessary for its survival". Sheftall wrote this way of viewing the "kokutai" as divinely sanctioned by a god-emperor led to a certain psychological in-balance as it was difficult for those who believed in the "kokutai" to accept any setback, which explains the immense rage that periodically erupted over any setback to Japan. In 1905, the Treaty of Portsmouth mediated by the American president Theodore Roosevelt ended the Russian-Japanese war, where Japan made gains, but nowhere near what was expected as the costs of the war had nearly bankrupted Japan, and thus the treaty was more favorable to Russia than it was assumed would be the case. The Treaty of Portsmouth led to anti-American rioting breaking out all over Japan and was presented in Japan as a national humiliation. 
Fukuzawa Yukichi was an influential author translator for the Japanese Embassy to the United States (1860). His 1875 "Bunmeiron no Gairyaku" (文明論の概略 "An Outline of a Theory of Civilization") contradicted traditional ideas about "kokutai". He reasoned that it was not unique to Japan and that every nation could be said to have a "kokutai" "national sovereignty". While Fukuzawa respected the Emperor of Japan, he believed "kokutai" did not depend upon myths of unbroken descent from Amaterasu.
Meiji Constitution.
The Constitution of the Empire of Japan of 1889 created a form of constitutional monarchy with the "kokutai" sovereign emperor and "seitai" organs of government. Article 4 declares that "the Emperor is the head of the Empire, combining in Himself the rights of sovereignty", uniting the executive, legislative, and judicial branches of government, although subject to the "consent of the Imperial Diet". This system utilized a democratic form, but in practice was closer to an absolute monarchy. The legal scholar Josefa López notes that under the Meiji Constitution, "kokutai" acquired an additional meaning.
 ;templatestyles src="Template:Blockquote/styles.css" / ;The Government created a whole perfect new cultural system around the Tennou [Emperor], and the "kokutai" was the expression of it. Moreover, the "kokutai" was the basis of the sovereignty. According to Tatsukichi Minobe, "kokutai" is understood as the "shape of the Estate" in the sense of "Tenno as the organ of the Estate", while the authoritarians gave the "kokutai" a mystical power. The Tennou was a "god" among "humans", the incarnation of the national morals. This notion of "kokutai" was extra-juridical, something more cultural than positive.
This stemmed from drafter Itō Hirobumi's rejection of some European notions as unfit for Japan, as they stemmed from European constitutional practice and Christianity. The references to the "kokutai" were the justification of the emperor's authority through his divine descent and the unbroken line of emperors, and the unique relationship between subject and sovereign. The "family-state" element in it was given a great deal of prominence by political philosophy. Many conservatives supported these principles as central to Nihon shugi (日本主義, "Japanism", or "Nihon gunkoku shugi", Japanese militarism), as an alternative to rapid Westernization. "Nihon shugi" is an ideology that values the traditional Japanese spirit and sets the tone of the state and society; it emerged in this period as a reaction to the Meiji government's radical Europeanization policy. Nihon shugi is a kind of "kukka shugi" (国家主義, lit. "statism" or "nationalism") ideology. "Nihon Shugi" opposed 'Europeanism' (欧化主義), democracy and socialism, which were considered unrelated to Japanese traditions, and during the Taishō and Shōwa era, it emphasized the "Kokutai" ideology centered on the emperor as opposed to Marxism.
Initially, perceived threats to the "kokutai" were seen as coming from abroad, but starting in the early 20th century there was a tendency to see threats to the "kokutai" as coming from within. The internal threats to the "kokutai" were seen first and foremost as class consciousness as Japanese peasants moved to cities to become the working class of the Japanese industrial revolution while other Japanese rose up to become a new middle class, both developments which were seen as threatening the "kokutai" between dividing Japanese society into classes with different interests. Other perceived threats to the "kokutai" were socialism and the rise of a trade union movement along with the rise of consumerism which were as seen as threatening the spiritual unity of the "kokutai". Finally, "Westernization" in a cultural sense was seen as damaging the "kokutai" by introducing foreign ideas into society. Paradoxically, the Russian-Japanese war emphasised these concerns about the cracks in the unity of the "kokutai" as it was believed that the principle reason for Russia's defeat was the gulf between the aristocratic officers of the Imperial Russian Army vs. the "salt-of-the-earth" common Russian soldiers, and that if a similar gulf were to emerge in Japanese society, then Japan too would be defeated in war. 
In 1910, the Army Minister Tanaka Giichi engaged in a project in "mass social engineering" by founding the semi-official "Zaigo Gunjin Kai" (Imperial Military Reserve Association) that worked closely with the Army Ministry to "spread militaristic thought among the population at large" as its founding charter put it. The purpose of the "Zaigo Gunjin Kai" was to solidify support for the "kokutai" as defined by the Imperial Japanese Army, which marked the beginning of the IJA as a political force. In 1915, the Imperial Military Reserve Association founded the Youth Associations designed to provide realistic military training for Japanese high school students. Later on in the 1920s, the Army Minister General Kazushige Ugaki founded the Youth Training Schools and the Attached Officer Program under which active duty serving officers worked as teachers in every elementary school and every high school in Japan. Under the Attached Officer Program, IJA officers taught the youth of Japan military tactics and drill, gymnastics and what Sheftall called "a heavy dose of indoctrination in ultra-nationalistic "kokutai" ideology under the guise of 'civics'". This militarization of the educational system led to a marked xenophobic and militaristic mood amongst the Japanese people who had been indoctrinated into believing to fight and die for the god-Emperor as the leader of the "kokutai" was their highest duty.
Taishō Democracy.
From the Xinhai Revolution to the enactment of the Peace Preservation Law (1911–1925), the most important pre-World War II democracy movement "Taishō Democracy" occurred. During the Taishō Democracy, the political theorist Sakuzō Yoshino (1878–1933) rejected Western democracy "minshu shugi" (民主主義 lit. "people rule principle/-ism") and proposed a compromise on imperial democracy "minpon shugi" (民本主義 "people based principle/-ism"). However, as Japanese nationalism grew, questions arose whether the "kokutai" emperor could be limited by the "seitai" government.
The Peace Preservation Law of 1925 forbade both forming and belonging to any organization that proposed altering the "kokutai" or the abolishment of private property, effectively criminalizing socialism, communism, republicanism, democracy and other anti-Tenno ideologies. The Tokkō ("Special Higher Police") was established as a type of thought police to investigate political groups that might threaten Tenno-centered social order of Japan.
World War II usage.
Tatsukichi Minobe (1873–1948), a professor emeritus of law at Tokyo Imperial University, theorized that under the Meiji Constitution, the emperor was an organ of the state and not a sacrosanct power beyond the state. This was regarded as "lèse-majesté". Minobe was appointed to the House of Peers in 1932 but forced to resign after an assassination attempt and vehement criticisms that he was disloyal to the emperor.
Great efforts were made to foment a "Japanese spirit" even in popular culture, as in the promotion of the "Song of Young Japan".
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The national debates over "kokutai" led the Prime Minister Prince Fumimaro Konoe to appoint a committee of Japan's leading professors to deliberate the matter. In 1937, they issued the "Kokutai no Hongi" (国体の本義, "Cardinal Principles of the National Body/Structure"). Miller gives this description. Increasingly, the "kokutai" was defined in militarised terms in the 1930s with calls being made for a "military nation" under which the entirety of the Japanese nation would be mobilised for war in peacetime with