The XYZ Affair was a 1798 iplomatic episode that worsened relations between France and the United States and led to the undeclared Quasi-War of 1798. John Jay's Treaty of 1795 angered France, which was at war with Great Britain and interpreted the treaty as evidence of an Anglo-American alliance. U.S. President John Adams and his Federalist Party had also been critical of the tyranny and extreme radicalism of the French Revolution, further souring relations between France and the States.