In Islamic tradition, the Caliph is the legitimate ruler of the entire political, religious, and social community of Islamic people. Caliphs exist in both the Sunni and Shiite tradition, however these two denominations disagree on how the Caliph should be chosen and who he is. The Caliph is said to govern the Ummah, or the community of Islamic worshippers in the world.

The Tang Dynasty ruled in China from 618 to 907 CE (not including the brief interruption of the reign of the Empress Wu Zetian). It succeeded the Sui Dynasty and was followed by the Five Dynasties and Ten Kingdoms period of Chinese history. During the initial rule of the Tang Dynasty agricultural land was redistributed and Confucianism was encouraged. The Tang Dynasty was one of the most successful in Chinese history and reigned over a relative golden age in Chinese history. Chinese territory expanded significantly during the Tang Dynasty as the conscripted forces conquered vast swathes of territory in Central Asia.

Political and state sovereignty in Europe in 1000 CE was mostly fragmented between a large number of elites who used private armies for coercion but did not regulate life in the ways that modern states do. Kingdoms and city-states that existed had little control of events that were outside of their immediate territories.

After the fall of the Tang dynasty in the early tenth century, the Chinese state fragmented into several smaller kingdoms. The largest of these was the Song, but they were never able to reunify China. China would finally be reunified in the thirteenth century under the rule of Kublai Khan and the Mongol Yuan dynasty.

The circle of justice was first developed in the Middle East during the classical era and was reinforced by the emergence of Islam in the seventh century. According to the circle of justice, a ruler owed justice to his subjects, his subjects paid taxes to the treasury, the treasury provided funding for the army, and the army protected the authority of the ruler. Collectively, it delineated the social duty and responsibility of all members of society and provided a unifying social force and justification for the rule of caliphs and emperors.

During the Heian period of Japanese history (usually referred to as Japan’s classical era), the emperor possessed almost no real power. He was a symbolic figurehead and a chancellor ruled in his place. The Fujiwara clan gained control of the chancellorship in the ninth century and ruled as Japan’s de facto ruling family until near the end of the Heian period.

During the High Middle Ages, England and France were the two most stable nations in Europe. In this case, “stable” means able to resist barbarian invasion and subject to fewer civil wars and power struggles between the upper classes.

Russia’s dynastic system is quite unique among the global history of dynasties, ruling families, and other related monarchical systems. Only two dynasties have ever ruled Russia: the (now infamous and much romanticized) Romanov dynasty and the Ruriks, who ruled the country before the Romanovs’ ascendency. The historical record is a bit murky as to the truth of the Rurik dynasty’s origins but they ruled over Russia for several centuries and are credited with establishing the tsarist system of government. This tsarism was later inherited by the Romanovs, who succeeded the Ruriks in 1613 and saw fit to maintain much of the Ruriks’ authoritarian tendencies.

Charlemagne's title as "Holy Roman Emperor" meant that his authority and empire were blessed by the Pope. This title asserted the power of the empire above other realms, and afforded them special privileges with regards to the pope and Catholic church. The Emperor had authority over legal and military affairs while the Pope maintained authority of spiritual matters.

The Holy Roman Empire was formed from the fragments of Charlemagne’s empire. It was an ethnically diverse and multicultural empire that stretched across much of central Europe. It was comprised of hundreds of small duchies and principalities, each of which retained some degree of autonomous power. It was not, however, ruled by a hereditary monarch until the Hapsburgs took effective control over the empire in the fifteenth century. Instead rulers were generally elected by those members of the nobility who were endowed as imperial electors.