History, if it's even close to a science, breaks down into two broad disciplines, one far more sciency than the other.
The more sciency one includes questions of fact, addressed by evidence like archaelogy, documents in archives, etc. There's hard evidence, which can overturn previous conclusions derived from less complete evidence, and any debate can be backed up by objective evidence. It addresses questions like the real author of a manuscript, the position of enemy lines in a battle, the identification of a discovered body, etc.
Then there is the less sciency one, consisting of theories about motivation, like what caused a war, or whether human behavior is primarily based on economics or something else, with occasional argument about who was "right," or "the best." No previous believed facts get overturned, usually, but instead a new theory is advanced to explain the old ones, and the theory is only defensible based on its own logic.