CHOISEUL, CESAR, DE (1598-1675), French mar shal and diplomatist, known for the best part of his life as the marshal du Plessis-Praslin, came of the old French family of Choiseul, which arose in the valley of the Upper Marne in the loth century. Entering the army he took part in the siege of La Rochelle, assisted to defend the island of Re against the duke of Buckingham, and accompanied the French forces to Italy in 1629. In 163o he was appointed ambassador at the court of the duke of Savoy, and was engaged in diplomatic and administrative work in Italy till 1635, when war was declared between France and Spain. Plessis-Praslin distinguished himself in the Italian campaign which followed, and after further service in Italy he was made a marshal of France (1645). During the first War of the Fronde he assisted Conde in the brief siege of Paris; and in the second war, remaining loyal to the queen-regent and the court party, he defeated Turenne and the allied Spaniards and rebels at Rethel (or Blanc-Champ) in 165o. He became minister of state in 1652, and in November 1665 was created duc de Choiseul. He was concerned in some of the negotiations between Louis and Charles I1. of England which led to the Treaty of Dover, and died in Paris on Dec. 23, 1675.