Thucydides

Thucydides (c. 460 B.C. - c. 400 B. C.) was a Greek historian and author of the classic History of the Peloponnesian War. This book is considered to be the first accurate historical narrative, following only the work of mortals, and not including any divine intervention. The book follows the Peloponnesian war, which lasted from 431 B.C. - 411 B.C., between Athens and Sparta. Thucydides himself lived in Athens, and his high family connections put him in constant contact with the main people in the war, which would write about.
In 424 B.C. he was appointed General and put in charge of seven ships to help defend the coast. However, this command was short lived, and he was exiled after he failed to save the city of Amphipolis from Spartan attack. Because of his exile, he was able to travel freely between both sides of the war, experiencing battle and meeting soldiers in both armies. This freedom enabled him to write his history far more accurately.
Thucydides narrative ends rather abruptly at the end of the war, in the year 411, leading many people to believe that he was killed before he could finish his book.

Source: http://en.wikipedia.org/wiki/Thucydides