Thucydides describes the rise of Hellas in preparation for war with great passion and enthusiasm as he was more capable of conjuring such a sight. For any single mind to experience the enormity of such an event is overwhelming and this is depicted in Thucydides historical account. The significance of experiencing factions unite with a common cause, factions who have remained segmented for years, is something that cannot be felt through words. It's with this experience, with this passion to explain and to record that Thucydides describes the onset of the war. Thucydides also uniquely combines interpretation with declaration: he writes the history as he believe it should be written; how he would have liked for things to have gone. He mixes eye witness testimony with passages of personal description which engenders an array of layers that can be focused on.
Thucydides also writes eloquently and descriptively, he gives example for his statements and he does not simply regurgitate facts. He is there to tell a story, and this is evident in his writing. It's enjoyable as Thucydides is quite a good orator. Thucydides describes the backstory of all the players, he describes what he knows about each through living his life amounts them. With his story comes thousands of voices, all of which have entered his head throughout his life. An entire civilization as seen from the eyes of a single human brings with it possibly biased information, but certainly a concrete, reliable understanding. One cannot know what it is like to be wrong, to experience being wrong, as being wrong is a state of ignorance, and when this ignorance is lifted with enlightenment, so is the state of being "wrong". So, we therefore understand that Thucydides brings with him a great (perhaps not veracious, however) understanding of his surroundings. With each character, Thucydides brings the story of their family. This accentuates the importance their culture puts on the family, which is something unique to Thucydides as one would only find such a writing characteristic (or the factual information to provide this characteristic) from a Greek writer. Thucydides is able to aptly describe the causes and effects of events as they unfolded before him. This fortunately does not leave for post-hoc inference and speculation as many other sources would.