Early societal groupings did not necessarily have a clearly defined central authority; on the contrary, there were in many instances separate leaders in terms of military needs, hunting, internal organisation within the society, religious and medical needs. As society became more complex and encompassed larger numbers of people, we can see a consistent trend towards development of a more centralised governing power, an executive authority.
Sri Aurobindo describes the beginnings of this process: “At first this authority was the king, elective or hereditary, in his original character a war-leader and at home only the chief, the head of the elders or the strong men and the convener of the nation and the army, a nodus of its action, but not the principal determinant: in war only, where entire centralisation of power is the first condition of effective action, was he entirely supreme. As host-leader, strategos, he was also imperator, the giver of the absolute command. When he extended this combination of headship and rule from outside inward, he tended to become the executive power, not merely the chief instrument of social administration but the executive ruler.”
This process did not develop easily or without setbacks. When Julius Caesar crossed the Rubicon and was considered a threat to the internal deliberations of the Roman Senate, noted citizens undertook to assassinate him! Yet, in subsequent years, the Roman Emperor, beginning with Augustus Caesar, gathered the reins of societal power and subordinated the alternative power centers within the Roman nation. Even when such a centralised control developed, it has not always remained stable, as other powers in the society put forth their claims for a voice, or even control over the decisions of the nation.
Even when the power of a strong central leader waned, however, the trend towards centralisation of power, possibly in a representative body, or a small ruling elite, has continued to develop in response to the need for prompt and effective action both internally and externally.
Sri Aurobindo, The Ideal of Human Unity, Part Two, Chapter 20, The Drive towards Economic Centralisation, pg. 178