Short answers, pulled from the story.
Thucydides was an Athenian historian and general born around 460 BC who wrote the History of the Peloponnesian War. He is called the father of scientific history because he applied strict standards of impartiality, evidence-gathering, and cause-and-effect analysis without attributing events to divine intervention, a method his contemporaries and later scholars recognised as a new departure in historical writing.
Thucydides was exiled because he failed to prevent the fall of Amphipolis to the Spartan general Brasidas in the winter of 424-423 BC. Athens blamed him for the loss of this strategically important city, even though Thucydides argued he had been unable to reach it in time. The exile lasted twenty years.
The Melian dialogue is a passage in the History of the Peloponnesian War in which Athens demands the submission of the island of Melos and dismisses appeals to justice as irrelevant between unequal powers. It is regarded as a foundational text of international relations theory and is widely studied in the context of political realism.
Thomas Hobbes translated Thucydides's History directly from Greek into English in 1628, making it the first English translation done from the original Greek. Hobbes, Thucydides, and Machiavelli are grouped together as founding figures of Western political realism.
Thucydides's narrative breaks off in the middle of the year 411 BC, leaving the final seven years of the conflict unrecorded. The traditional explanation is that he died while writing, though other explanations have been proposed. The History was later subdivided into eight books, most likely by librarians and archivists working in the Library of Alexandria.
Thucydides confined himself to contemporary political and military events based on firsthand eyewitness accounts and excluded geography, ethnography, fables, and moral judgment from his text. Herodotus, by contrast, recorded ethnographic information, fables, and geographical observations, presented conflicting accounts without resolving them, and viewed history as a source of moral lessons. Thucydides also did not acknowledge divine intervention, while Herodotus often attributed events to the wrath of the gods.