Most doctoral dissertations in history begin with a discussion of previous work on whatever the topic may be, so it may be helpful to search Dissertation Abstracts (ProQuest Digital Dissertations) for a recent dissertation on your topic. In general, dissertations written after 1995 will be available in full text.
A good textbook or introduction to a topic may have a bibliographic essay -- sometimes at the back, under the title "Further Reading." When well done, this can be extremely helpful in getting oriented to the literature on your topic.