After the fall of the Western Roman Empire several kingdoms were formed, but had short lives, being the kingdom of the Franks the only ones to stand out. The first king of the Franks to unite all the barbaric nation was Clovis who reigned between 482 and 511, but Charlemagne was around the ninth century which reached the apogee of his kingdom was appointed by Pope Leo III the new Roman Emperor of the West. After the death of Charlemagne, his kingdom is divided into three, then Europe is fragmented into several small kingdoms helping in the formation of feudalism.
The European feudalism, however, presents quite different between the ninth century, when small farmers are urged to protect themselves from enemies near the castles, and the thirteenth century phases, when the feudal world knows its heyday to decline below.
The weakening of the feudal system and the strengthening of the bourgeoisie were instrumental in the creation of modern European states, for example, Portugal , Spain, France and England.
After the failed claim of the Church of Rome to unify the continent under his baton, the different European peoples began to unite around a great leader who was stronger than regional leaders to unify the diverse and fragmented regions which formed the "patchwork" that was the European map of the time.
With this new socio-political setting, the kings began to take a close profile of absolutism, which peaked with Louis XIV, and through this power of the monarch, subjugating the local leaders is that the modern nation state as we know it today might arise.
With the exception of the Holy Roman Empire, and the Italian States, which continued to maintain a medieval structure, fragmentation into mini states within a community until about the nineteenth century, throughout Europe gradually started walking toward the construction of modern states we know today, the first of which Portugal in 1139, a result of the Christian reconquest of the Iberian Peninsula.
Important to note that the bourgeoisie of the time gave the decisive support for national states were formed. The strength of local leaders was a rather negative for the development of trans-European trade and financial activities hurdle, since each local lord established their own taxes, laws and regulations.
The centralized power obviously interested the monarch, particularly because the new order brought his political empowerment, greater performance and greater administrative independence of the church.
So the king could exercise freely within his realm their beliefs, ideas and values, something that before the rise of the nation state was hampered by the action of regional leaders. It is therefore natural that occurred an alliance between kings and bourgeoisie, because freedom of action provided that the new situation was extremely advantageous to both.
To consolidate this reality was needed to form a political and administrative bureaucracy, as well as a national army, work to be financed by taxes levied on the population, in addition to funding provided by wealthy bankers and merchants. With these major funding these early capitalists become patrons of the state receiving commercial and customs advantages, thus, a class was based on the other, ensuring the reality that allowed a class the existence of the other.
On the other side, the old local feudal lords begin to form the class of the aristocracy, in order to maintain the status quo, it was virtually "sustained" by the monarch and the bourgeoisie, thus keeping the kingdom in peace, free from internal conflicts. This situation turned these noble a parasitic class, which in fact, contributed nothing to the social and economic advancement of the kingdom, living off of this.
This contradiction in the social system of the nation state would go into crisis by the eighteenth century, time of the French Revolution and American independence, where the situation of the nobility of parasitism caused an unsustainable situation, which drained the wealth of the state, maintaining population in a state of unacceptable poverty, ultimately causing the extinction of the absolutist state, with a strong monarch.