Even Boris Godounoff is to us more a picture out of a book, like the Macbeth whom he so strongly resembles from a theatrical point of view, than the monarch who had a large part in the making of the Russian people.

The Roman censorship prevented us long ago from making the acquaintance of the Gustavus of Sweden whom Ankerstrom stabbed to death at a masked ball, by transmogrifying him into the absurdly impossible figure of a Governor of Boston; and the Claudius of Ambroise Thomas's opera is as much a ghost as Hamlet's father, while Debussy's blind King is as much an abstraction as is Melisande herself.
Operatic dukes we know in plenty, though most of them have come out of the pages of romance and are more or less acceptable according to the vocal ability of their representatives.

When Caruso sings "La donna e mobile" we care little for the profligacy of Verdi's Duke of Mantua and do not inquire whether or not such an individual ever lived.
Moussorgsky's Czar Boris ought to interest us more, however.

The great bell-tower in the Kremlin which he built, and the great bell--a shattered monument of one of his futile ambitions--have been seen by thousands of travellers who never took the trouble to learn that the tyrant who had the bell cast laid a serfdom upon the Russian people which endured down to our day.

Boris, by the way, picturesque and dramatic figure that he is as presented to us in history, never got upon the operatic stage until Moussorgsky took him in hand.