Astatement, especially in diplomatic negotiations, that expresses or implies the threat of serious penalties if the terms

The answer is ultimatum. Generally, an ultimatum is the final call in a succession of requests. A limited time for the fulfillment of the request is set and there is no room for further negotiation.There will be consequences as a result of the non-acceptance of terms.

In 911, a group of vikings lead by rollo besieged paris and chartres. after a victory near chartres on 26 august, charles decided to negotiate with rollo. the talks were led by hervé, the archbishop of reims. this resulted in the treaty of saint-clair-sur-epte, which granted rollo and his soldiers all the land between the river epte and the sea. it also granted him brittany, "for his livelihood". at the time, brittany was an independent land which france had not been able to conquer. in exchange, rollo promised the king his loyalty and military assistance when needed. also rollo also agreed to be baptised and to marry gisela, the king's daughter. the territory given rollo is about the same as upper normandy. this would grow to become normandy under rollo's descendants. - wikepedia