If France decides to join the United States in a strike against Syria, it would be the first time American and French forces have conducted a joint military operation since the Siege of Yorktown at the end of the American Revolutionary War.
France and the U.S. have had their famous disagreements over military action, most notably the Iraq war and France's decision to leave Afghanistan before NATO and U.S. troops planned their drawdown. The two countries have also had some near-misses on joint operations. For example, in 1954, U.S. forces proposed an operation that would have saved French forces in the Battle of Dein Bien Phu against Communist militants in Vietnam. American planes would have taken off from bases in the Philippines. But the political risks of getting involved in the fight were too much for President Eisenhower, and he nixed the operation, called Operation Vulture.
Indeed, the United States and France have been allies in different conflicts throughout history. But the two nations have not gone after a target alone together since the War of Independence. And it just so happens to have been at the final decisive victory at Yorktown, Va.
France came to the side of the Americans during the Revolutionary War following the colonials' victory at Saratoga. The French, attempting to become the military power of Europe over Britain, signed the Treaty of Alliance in 1778, ushered through by Benjamin Franklin.