Diplomacy is a game of negotiation and tactics leading to some grand strategy. Periodically this will lead to one player reneging on an agreement with another, in favor of greater tactical advantage. A direct assault on a former ally that leaves his rear open, or the total reversal of an alliance, is referred to as the stab.
Here’s something I’ve observed enough to think it’s a trend: at least among the players in my server’s pool, there is a lot of weak stabbing, almost seemingly for the sake of stabbing, as if pulling off the most obnoxious betrayal were the method of winning the game. Shae and I both agree on this, and I’m paraphrasing the single best advice he’s given me as a player:
Under no circumstances should you stab another player unless it will lead to the solo, or it will remove that player from the game in short order.
I have italicized and boldfaced the above quote because it should be the mantra of any player about to attempt a stab. After a protracted, careful consideration of the dynamics of the board, if you decide to stab a player, one of those two outcomes should be the result. Much, much more will be written about the art of the stab later on, but this one rule should be taken as absolute gospel by every single player who is serious about being good at Diplomacy.