Nicolò Machiavelli
The first great political philosopher of the Renaissance. His famous treatise The Prince (Il Principe), written in 1512, stands apart from all other political writings of the period insofar as it focuses on the practical problems a monarch faces in staying in power, rather than more speculative issues explaining the foundation of political authority. As such, it is an expression of realpolitik, that is, governmental policy based on retaining power rather than pursuing ideals.
No less so for The Art of War (Dell'arte della guerra), which is presented as a discussion among Machiavelli's friends; a dialogue between the condotierri captain, Fabrizio Colonna, and each of the others in turn acting as questioner. It is a technical treatise different from The Prince in that it discusses politics specifically related to warfare. Written in 1521, The Art of War is a first full scale modern attempt to revive classical military thought.