I say this, because of a recent post on so-called "Gentlemen's Diplomacy," a tenet of which is stabbing when the moment is right, regardless of the players or agreements made. I realize that is the nature of a stab, and stabbing is often a key to the game, but lying in this way can hardly be categorized as "gentlemanly." I prefer to deceive without lying.
e.g- In a recent game as Russia I had pieces in War, Gal, Bud, Rum, Sev, and BLA. Here's the deal I cut with austria. If they supported Rum-Bul, then I would move Bud-Rum, Sev and BLA would fight the Turks, and Galicia would move westward. I also was careful to note that we were almost certain to still come to blows, and any future fighting was reasonable, so long as we kept to the agreement.
When adjudication came, I moved Rum-Bul (with austrian support), Bud-Rum, Sev and BLA worked on the turks, but War-Gal and Gal-Vie! Well I'm sure it's not what austria had in mind, nor what they presumed was the meaning of "move westward," but I stayed true to my word nonetheless.
THAT is diplomacy.