Some people have asked me for research paper topics. I am reluctant to suggest topics, since I think a successful research paper is most likely to result from your own search for an refinement of a topic. All other things being equal, it is preferable to go into more depth about a specific topic than to cover a broad subject superficially. Your paper should have a specific point if not necessarily an argumentative thesis, then at least a central argument, claim, etc.
Proof is very, very hard to come by in historical study.
A successful research paper provides evidence that the author has an adequate knowledge of relevant source material. As a very rough rule of thumb in my own writing, I expect to actually use in the paper at least as many sources as there are pages. If you are unsure whether or not to include a citation, include one. As noted on the syllabus , you should aim at a paper of 7-10 pp. But having something coherent to say is more important than filling up a given number of pages.