The era immediately following the Greek Classical era is called Hellenism. It begins with the campaigns of Alexander the Great in the year 334 B.C.E, and ends with the establishment of a Roman protectorate in Ptolemaic Egypt in 30 B.C.E. The Hellenism was shaped by the cultural exchange with the areas conquered by Alexander the Great, the Romans, the Carthaginians, and the Galatians and Celts from the Danube river. Bigger kingdoms and states dominated the political landscape instead of the Classical Polis. Although many Poleis were founded in the Hellenistic era, they were usually not independent, but under a protectorate of a bigger party. At the end of Hellenism, the Republic of Rome dominated the whole Mediterranean, and the formerly massive empire of Alexander the Great was no longer under Greek influence.
After his father, Philip II of Macedonia, established his dominance over the Greek states, Alexander the Great was able to start his campaign against the Persian empire. After only eleven years, the whole of Asia Minor, Persia, Egypt, and parts of Afghanistan, Arabia, and even India were brought under Macedonian control. The sudden death of Alexander created a power-vacuum, and consequently a fierce dispute erupted about his succession. His territories fell apart into various successor-kingdoms, the so called Diadochi. The following half century was shaped by the bloody struggle of the Diadochi for over the succession of Alexander. After no less than six wars of the Diadochi, the dynasties of the Ptolemies in Egypt, the Seleucids in Syria, and the Antigonids in Macedonia, established themselves. The balance of power stabilized a bit after that and each of the dynasties went to follow their own agenda. With the exception of the campaigns of Pyrrhos, and the Celtic invasion in central Greece, power struggles between Hellenistic states were dominating the third century B.C.E. The second century saw Macedonia fall under Roman control after three wars, and soon after that become a Roman province. Over the following century, the Romans were able to establish themselves as the master of all the remaining Hellenistic kingdoms.