The XYZ Affair was a political and diplomatic episode in 1797 and 1798, early in the administration of John Adams, involving a confrontation between the United States and Republican France that led to an undeclared war called the Quasi-War. 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 documents released by the Adams administration.