I'm writing a history paper, and im looking for specific reasons that I could write about in Genghis Khan and his reasoning for expanding into China, I'd love if you'd recommend an article or a book I could learn more of it about from, the mongols are quite interesting.
Hello there. Your question seems to be related to school work, any potential respondents, that our rules DO permit people to ask for help with their homework, so long as they are seeking clarification or resources, rather than the answer itself. Which seems to be exactly what you are doing! This policy is further explained in this META Thread.
Additionally, while our users may be able to help you out here, we hope that you also will take the time to check out our six-part series, "Finding and Understanding Sources", which should hopefully prove to be helpful for you as you continue in your research.