Evolution of international state system

EVOLUTION OF INTERNATIONAL STATE SYSTEM
Through time the international system has undergone considerable change and evolution. The city states that were characteristic of ancient Greece, the feudal principalities that defined Europe in the Middle Ages, and the empires that have existed throughout recorded history (both Eastern and Western) have largely been replaced by the nation-states as the dominant actors within the international arena.
The state system was based on the idea that by concentrating power in a single head or center, the state itself could be sufficiently controlled and its environment sufficiently managed to achieve self-sufficiency or at least a maximum of self-sufficiency in a world which would inevitably be hostile or at best neutral toward each state's interests and in which alliances would reflect temporary coalitions of interests that should not be expected to last beyond that convergence.
In the subsequent paragraphs a brief account of evolution of state system is given.
The Medieval Background (Middle Ages: An Age of Faith 500 A.D. to 1500 A.D)
The Medieval Synthesis refers to the relationship between the

Germany, Italy and Australia formed triple alliance 1882 in order to maintain status of quo of 1871. Great Britain, France and Russia formed triple entete (1907). In First World War the Austro-Hungarian, Turkish, and czarist were eliminated and Japan was confined to Far East.

Ferdinand of Aragon married Isabella of Castile and their marriage produced the modern state of Spain. Charles V(Charles I of Spain) 1516-1556 abdicates and divided his possessions between his son Philip II, 1556 - 1598, who got Spain, Spanish colonies, and the Netherlands while his brother Ferdinand I, 1556 - 1564, who got Austria and also the nominal title of Holy Roman Emperor.

This war disturbed the balance of power which was restored in 1763. British, Russia. Sweden defeated the Corsican adventure. The war ended with the Treaty of Paris, signed in 1763.

The Dominance of Spain and its Habsburg Rulers(1492 – 1648)

Balance of power became a global and multicentric phenomenon instead of confining to Europe and only being unicentric.

In the Balkans Greece, Rumania, Serbia, Bulgaria and Albania became sovereign states. New states joined America and it was recognized as major power after American Spanish war of 1898. Japan also joined in as one of the eight major powers of this arena.

Collective defense also became international phenomenon with Asian nations getting importance. Institutions like foreign policy, diplomacy, war etc were subjected to democrization. Discovery of nuclear weapons and phenomenon of Cold War originated.