Most PhD history programs require students to be proficient enough in a second language to translate a one page passage of text into English. Many even require a third. Which languages a student is expected to know usually depends upon his or her proposed course of study.
At some of the more prestigious institutions, someone studying French history would generally be expected to know English, French and German. Someone studying Chinese history would need to know two Asian languages. This makes sense, as anyone claiming to be an expert on a given topic best be able to read primary sources in the language they were written.