Which preposition to use with obsess

with Occurrences 25%

Thus ended the last hope of the Crown Prince of Germany, who apparently was obsessed with the desire to conquer Verdun, in the neighborhood of which thousands of the flower of the German army found only a burial place, without any laurels of victory.

for Occurrences 2%

There are no words severe enough for Mrs. Oliphant's horrible portrait of her as a plain-faced, lachrymose, middle-aged spinster, dying, visibly, to be married, obsessed for ever with that idea, for ever whining over the frustration of her sex.

Which preposition to use with  obsess