I had to chuckle when I read this one. Beyond teaching history ...there are few if any real "career tracks" for history majors. While many eventual law students have studied history, poli sci, other social sciences and humanities those have little or nothing to do w/ the study of law. One can go that route w/ virtually any major ...accounting, computer sci, engineering, business, econ, and on and on. The point is law is not dependent upon history. Rather, history might depend upon the study of law. One certainly cannot go into an MS or Ph.D. in comp sci, EE, physics, PT, med school, or any other area requiring specific competencies and or even general knowledge and background. I love history, study it constantly, but as an area of study to prepare one for a specific field of work? Ask any American history major ...
EXCEPT for history major at USNA or one of the other SAs. This area of study and the BS degree and concurrent commission provide so many specific areas of work it is almost unfathomable.
I fear the OP is looking at this from the wrong perspective. One exception. If he wants to be a lawyer. But that has literally nothing to do with studying history. btw, the answer is NOT the same for poli sci @ USNA. That is a major of a very different color.
Now, taking a different tack ...there are MANY jobs in USN that might well be served by an indepth knowledge of history, virtually none that would REQUIRE having a major in history. None of those jobs will be much available to a junior officer.