When Sparta launched her invasion of Athens, it was also hit by a dreadful illness that began in 430 BCE and spread across the city-state for a period. The epidemic claimed the lives of around one-third of Athens’ population. When its Spartan adversaries eventually defeated Athens during the Peloponnesian War, this played a role: After the epidemic had killed so many lives, Athens was unable to assemble the military leadership and might that it required to resist the increasingly strong Peloponnesian League, and the city-state was forced to surrender. Athens was in ruins at the conclusion of the fighting, which occurred in 404 BCE Sparta rose to become the most powerful city-state in the ancient Greek world. Wars between the city-states raged on for a little longer, until Thebes ultimately overcame Sparta in 371 BCE. Greece’s economic situation deteriorated because of the prolonged conflict, and the divide between affluent and poor grew. The civic spirit that had been the hallmark of Greece’s golden era had all but vanished by the end of the century. The city-states, in short, were no longer the illustrious entities that they had previously been. Greece’s northern neighbor, Macedonia, was becoming increasingly strong at the same time that the Greek city-states were declining, according to historians. Macedonian king Philip II launched an invasion of Greece in 353 BCE. The conflict that occurred did not conclude until Greece was ultimately overrun in 338 BCE, though. Despite the Macedonian triumph, Philip felt that a united Macedonian-Greek army would be able to overcome the mighty Persians in the end. He, on the other hand, was not to see this. The death of Philip II by a Macedonian in 336 BCE resulted in the succession of his son, Alexander, who was just 20 years old at the time and who history would come to refer to as “the Great.” Alexander followed out his father’s plan to attack Persia, and he was praised for it. As a result, two years after Philip’s death, Alexander launched a 10-year war that culminated in his conquest of the Persian Empire. Alexandra had conquered most of the known globe by the age of thirty, stretching his kingdom from Egypt to India and establishing a stronghold in the Mediterranean.