You can specialize in whatever you want, but it's hard to really, genuinely specialize in two disparate areas like that. Becoming a specialist in an area requires a ton of reading to become familiar with the historiography and stay up to date on the latest research, which as you can imagine is quite time-consuming. To do research in those areas, you'd also need to acquire the requisite language skills and become familiar with the primary sources you use in those areas, in addition to being familiar with the historiography, which would consume even more of your time. From a practical perspective, it's easier to specialize in one area or maybe two closely-related areas, since there are only so many hours in the day and becoming an expert in even one area requires a lot of work.

If you're just going to major in history in undergrad or whatever, then this isn't that big of a deal. You can take classes in both areas if they interest you and be fine. You don't really need a super-deep understanding of the historiography to do that, and you probably won't need to be fluent in the language(s) either. However, if you decided to go on to graduate study in history, which you should not do, you would probably need to pick one or the other to specialize in because of the aforementioned time constraints. Most schools require you to take one or two minor fields in addition to your major field for your comprehensive exams, and that's one way to incorporate an area of interest outside your primary field (I did one of my minors in Middle Eastern history, for example), but in the end you're going to have to pick one as your major field and the field in which you're going to do a dissertation, unless you come up with a project which encompasses both of them, but that might be difficult to do for the aforementioned reasons. I'm not a professor anymore so I can't really speak to how having two disparate fields like that would play in the job market, but it doesn't really matter since there are no jobs anyway.