I am having trouble understanding why is Wen used in this question instead of Wer.
Wen nannte man den eisernen Kanzler?
Wen is used to ask for a direct object (accusative), but it looks to me in this example that the question is referred to the subject of the sentence, that is who is the person doing the action of calling himself the Iron Chancellor. Then why is it not
Wer nannte man den eisernen Kanzler?
In this other sentence:
Wen hast du gesehen? Ich haben meinen Bruder gesehen, clearly Wen is asking about the object, since the subject is "Ich".
In the previous sentence, how would I formulate a long answer, to help me see why it is accusative?
Man nannte Otto den eisernen Kanzler
Note: I suspect the impersonal "man" here may be confusing me.