As many others have pointed out, Machiavelli is unique in being the first (known) political thinker to consider the modern idea of the nation-state and the notion of sovereignty. However, there is another important distinction to make.
While there were other post-Hellenic philosophers who wrote in the field of politics (Augustine may be one), these were all philosophers first who arrived at political theory only as a consequence of their politics. Machiavelli, on the other hand, was the first to approach political science as a independent discipline, concerned with the art of politics rather than the ethic