How was Thucydides work different from previous historians?

One of the greatest ancient historians, Thucydides (c. 460 B. C.-c. 400 B. C.) chronicled nearly 30 years of war and tension between Athens and Sparta. His "History of the Peloponnese War" set a standard for scope, concision and accuracy that makes it a defining text of the historical genre. Unlike his near-contemporary Herodotus (author of the other great ancient Greek history), Thucydides’ topic was his own time. He relied on the testimony of eyewitnesses and his own experiences as a general during the war. Though specific in detail, the questions he addressed were timeless: What makes nations go to war? How can politics elevate or poison a society? What is the measure of a great leader or a great democracy?