The answer is the The XYZ Affair. It was a a political and diplomatic incident between French and United States diplomats in 1797 and 1798 early in the administration of John Adams that resulted in a limited, undeclared war known as the Quasi-War. U.S. and French negotiators bring back peace with the Convention of 1800, also known as the Treaty of Mortefontaine. The name derives from the substitution of the letters X, Y and Z for the names of French diplomats Hottinguer (X), Bellamy (Y), and Hauteval (Z) in official papers released by the Adams administration.