Árpád was the Magyar leader whom sources name as the single leader who unified the Magyar tribes via the Covenant of Blood (Hungarian: Vérszerzodés), forging what was thereafter known as the Hungarian nation. Árpád led the new nation to the Carpathian Basin in the 9th century. From 895 to 902 the whole area of the Carpathian Basin was conquered by the Hungarians.
After that, an early Hungarian state (the Principality of Hungary, founded in 895) was formed in this territory. The military power of the nation allowed the Hungarians to conduct successful fierce campaigns and raids as far as today’s Spain. A later defeat at the Battle of Lechfeld in 955 signaled an end to raids on western territories (Byzantine raids continued until 970), and links between the tribes weakened.
The ruling prince (fejedelem) Géza of the Árpád dynasty, who ruled only part of the united territory, the nominal overlord of all seven Magyar tribes, aimed to integrate Hungary into Christian Western Europe, rebuilding the state according to the Western political and social model.
He established a dynasty by naming his son Vajk (the later King Stephen I of Hungary) as his successor. This was contrary to the then-dominant tradition of the succession of the eldest surviving member of the ruling family. By ancestral right prince Koppány, -as the oldest member of the dynasty- should have claimed the throne, but Géza chose his first-born son to be his successor.
The fight in the chief prince’s family started after Géza’s death, in 997. Duke Koppány took up arms, and many people in Transdanubia joined him. The rebels represented the old faith and order, ancient human rights, tribal independence and pagan belief, but Stephen won a decisive victory over his uncle Koppány, and had him executed.
Stephen was crowned by the Holy Crown of Hungary in December 1000 AD in the capital, Esztergom. The Papacy confers on him the right to have the cross carried before him, with full administrative authority over bishoprics and churches. By 1006, Stephen had solidified his power, eliminating all rivals who either wanted to follow the old pagan traditions or wanted an alliance with the Eastern Christian Byzantine Empire. Then he started sweeping reforms to convert Hungary into a western feudal state, complete with forced Christianity.
Stephen established a network of 10 episcopal and 2 archiepiscopal sees, and ordered the buildup of monasteries churches and cathedrals. In the earliest times Hungarian language was written in a runic-like script. The country switched to the Latin alphabet under Stephen.
From 1000 to 1844, Latin was the official language of the country. He followed the Frankish administrative model: The whole of this land was divided into counties (megyék), each under a royal official called an ispán count (Latin: comes)—later foispán (Latin: supremos comes). This official represented the king’s authority, administered its population, and collected the taxes that formed the national revenue. Each ispán maintained an armed force of freemen at his fortified headquarters (castrum or vár).
What emerged was a strong kingdom that withstood attacks from German kings and Emperors, and nomadic tribes following the Hungarians from the East, integrating some of the latter into the population (along with Germans invited to Transylvania and the northern part of the kingdom, especially after the Battle of Mohi), and conquering Croatia in 1091. According to an alternative history based on the document Pacta Conventa, which is most likely a forgery Hungary and Croatia created a personal union. There is no undoubtedly genuine document of the personal union, and medieval sources mention the annexation into the Hungarian kingdom.
After the Great Schism (The East-West Schism; formally in 1054; between Western Roman Catholic and Eastern Orthodox Christianity.) Hungary determined itself as the easternmost bastion of Western civilization (This statement was affirmed later by Pope Pius II who wrote that to Emperor Friedrich III, “Hungary is the shield of Christianity and the protector of Western civilization”).