Fait accompli is "a thing accomplished and presumably irreversible." 
Fait accompli negotiation tactic
The website of the noted negotiation expert Dr. Chester L. Karrass declares:
|“|| Fait Accompli Tactic
"Someone takes a surprise action designed to place them in a favorable negotiating position. The 'accomplished fact' affects the final outcome of the negotiation because it alters the balance of power. The strength of fait accompli rests in the fact that once a deed is done, it is difficult to undo."
An example of fait accompli being used in political negotiations is the continual building of Jewish outposts and settlements in disputed territory while Jewish/Arab political negotiations occur in order to create "facts on the ground".