Thucydides was a great Greek historian, he wrote the History of the Peloponnesian War that is divided into eight books and recalls the struggle between Athens and Sparta.
He wrote the eight books from his experience of the war writing only about the timeline he lived and introduced a contemporary style to the genre in a sharp and polished way. He based his story on the facts, events, dates and personalities only and left behind the religious and supernatural facts others wrote about. This is why he's writing is different from others, specially Herodotus.
Thucydides eight-books ended abruptly as if one day he couldn't write anymore.