Here is the sentence:
"General Martin Dempsey, the Joint Chiefs of Staff chairman who just wrapped up a visit to Afghanistan, was asked whether he foresees North Korea taking military action soon.” Source(https://www.dailywritingtips.com/appositive-phrases-punctuation-problems/)
Here is the revised sentence
“General Martin Dempsey, the Joint Chiefs of Staff chairman, who just wrapped up a visit to Afghanistan, was asked whether he foresees North Korea taking military action soon.”
The explanation is by combining the general’s title with the reference to his recent visit to Afghanistan, the sentence implies that more than one Joint Chiefs of Staff chairman exists; Dempsey is the one who had just returned from Afghanistan. The phrase “the Joint Chiefs of Staff chairman” must be bracketed by a pair of commas to show that it is the first of two parenthetical phrases dividing the subject from the object: “General Martin Dempsey, the Joint Chiefs of Staff chairman, who just wrapped up a visit to Afghanistan, was asked whether he foresees North Korea taking military action soon.”
Can someone explain to me the explanation? I just don't get it because there is only one chairman so even without a comma the sentence still makes sense to me.