Ancient Greece's Mediterranean hegemon

This is an era of multiple powers rising: the vast Persian Empire, the military-oriented Sparta, the commercially dominant Athens, the up-and-coming Thebes, the ambitious Macedonia, the two powers of the western Mediterranean, and the newly emerging Rome...

This is an era where stars shine brightly: Agesilaus, the last king of Sparta; Epaminondas, the renowned general who propelled Thebes to prominence; Philip, the founding ruler who laid the foundation for Macedonian hegemony; Dionysius, the tyrant of Syracuse; Camillus, the dictator who saved Rome...

This is an era of intellectual discourse: the great philosopher Plato, the founder of the Cynic school Antisthenes, the Pythagorean school with its focus on numbers as divine, the encyclopedic scholar Democritus, the father of Western medicine Hippocrates, the renowned playwright Aristophanes...

As the protagonist traverses through reincarnation, arriving in this era as a humble mercenary, what will he bring to this world?