Thucydides, (460?–;400? B.C.), an Athenian general and historian. He is known for his History of the Peloponnesian War.This account of the struggle (431–404 B.C.) between Athens and Sparta and their respective allies has won him the title “father of scientific history.” His emphasis on accuracy and his impartial attitude in reporting events and drawing conclusions marked a new approach to the writing of history. He included only what he knew to be true, based on his own notes written during the early phase of the war, in which he participated, and on interviews with persons who had taken part in other actions.

Thucydides believed that studying events of the past could help people understand similar events in the future. From the onset of the Peloponnesian War he recognized the significance of the conflict, which eventually toppled Athens from its preeminent position among the Greek city-states. Thucydides saw greed for power as the underlying cause of the war. He wrote in a somber tone, realizing that Athens had abused its great power and anticipating that it would as a result be defeated.

In one respect Thucydides departed from his usual accurate writing. When reporting a public speech, by his own admission he supplied the words himself. Although endeavoring to give the true content of the speech, he often composed it in a graceful style that the original may have lacked.

Little is known of Thucydides' life. He was born into a wealthy Athenian family and as a young man was a follower of the statesman Pericles. During the early years of the Peloponnesian War, he was one of Athens' generals. In 424, however, he failed in an attempt to save the city of Amphipolis from capture and was exiled for the remainder of the war.

For the next two decades Thucydides traveled through Greece, talking with eyewitnesses of the war's events and writing his great work. He probably returned to Athens in 404. His Historycovers the war only to 411; it is presumed that Thucydides died before he was able to complete it.