Which preposition to use with ressort

of Occurrences 3%

Anything so thoroughly realistic that, as President Durand said, "The stones seemed to be, not painting, but the real thing," puzzled the ordinary picture buyer; and the American Art Union, which was the principal buyer of the day, and the dernier ressort of the young artist, was managed by a committee of ordinary picture buyers.

Which preposition to use with  ressort