The XYZ Affair is 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 leads 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.

An American diplomatic commission is sent to France in July 1797 to negotiate problems that were threatening to break out into war.

The diplomats, Charles Cotesworth Pinckney, John Marshall, and Elbridge Gerry, are approached through informal channels by agents of the French Foreign Minister Talleyrand, who demands bribes and a loan before formal negotiations can begin.

Although such demands are not uncommon in mainland European diplomacy of the time, the Americans are offended by them, and eventually leave France without ever engaging in formal negotiations.

Gerry, seeking to avoid all-out war, remains for several months after the other two commissioners leave.

His exchanges with Talleyrand lay the ground work for the eventual end to diplomatic and military hostilities.

The failure of the commission causes a political firestorm in the United States when the commission's dispatches are published.

It leads to the undeclared Quasi-war (1798 to 1800).

Federalists, who control the government, take advantage of the national anger to build up the nation's military.

They also attack the Jeffersonian Republicans for their pro-French stance, and Elbridge Gerry (a nonpartisan at this time) for what they see as his role in the commission's failure.