Definition of "diplomatist"

It was not so easy to penetrate the motives of the Pawnees. Calm, dignified, and yet far from repulsive, they set an example of courtesy, blended with reserve, that many a diplomatist of the most polished court might have strove in vain to imitate.

1827, [James Fenimore Cooper], The Prairie; a Tale. […], volumes (please specify |volume=I or II), Philadelphia, Pa.: Carey, Lea & Carey […]

Diplomatists have no right to complain of mere lies; it is their own fault, if, educated as they are, the lies deceive them; but they complain bitterly of traps.

1918, Henry Adams, The Education of Henry Adams‎