Being the direct descendant of Rochambeau, known hereabout as the Maréchal, for the title of field marshal that was bestowed on him by Louis XVI on his return from America, would be almost a full-time occupation. But the count has supplemented it with the role of a kind of representative of trans-Atlantic relations, which he and his wife, Madeleine, have taken particularly to heart in recent years, when ties between Washington and Paris have been strained. (Those relations have been getting better. And some hope that the recent election of the moderately pro-American Nicolas Sarkozy as president of France may further improve them.)

Whatever the differences, they are not preventing the count and his family from playing host this summer to a Rochambeau festival to celebrate the 200th anniversary of the Maréchal’s death in 1807 — marked by small French and American flags along roads leading to the chateau — with conferences, lectures and 18th-century cultural events, including a production of Mozart’s “The Magic Flute,” in the chateau courtyard.

“The circumstances of the American Revolution merit being understood by the French,” said Darien Basset-Geraghty, an American neighbor of the Rochambeaus’ who is the director of the festival. “The formation of our country is complicated,” she said. “Rochambeau himself noted how the colonists, while casting off the English crown, kept their slaves.”

The count was born 90 years ago in Paris, where his father, an officer in the French Army, had gone for his career, leaving the chateau and its upkeep to a brother, who died in 1919, but whose widow stayed on until her death in 1949. The count’s aunt had little means to maintain the chateau, just outside the quaint village where Rochambeau is buried, especially during World War II, when German officers were for a time billeted in its rooms. (They left because it lacked central heating, the count said with a chuckle. He recalled once surprising a circle of Germans in an upper room, huddled around a ring of candles to keep warm.)

The original chateau was built in the 16th century. “It was a small Renaissance chateau,” the count said, seated in a former dining room, decorated with wall paintings representing the hunt, a family pastime. “The Maréchal enlarged it by the addition of two wings.” One now houses the count and his wife, the other a daughter and her family. (Central heat was added in the 1950s.)

The Maréchal typically kept a home in Paris to be nearer the royal court at Versailles. He was a settled veteran of 55 when in 1780 the king asked him to lead an expeditionary force of 5,500 men to North America to support the colonists in their uprising against the British king. The French, who had only a few years earlier lost most of their colonies in North America to the British, and a few years hence would lose their king to the guillotine, apparently reasoned that the enemy of their enemy should be their friend....