[108] Frustrated by the perceived lack of commitment on the part of the French, Adams wrote a letter to French foreign minister Vergennes in December, arguing for French naval support in North America. Franklin toned down the letter, but Vergennes still ignored it.[109] In September 1778, Congress increased Franklin's powers by naming him minister plenipotentiary to France while Lee was sent to Spain. Adams received no instructions. Frustrated by the apparent slight, he departed France with his son John Quincy on March 8, 1779.[110] On August 2, they arrived in Braintree.[111]

Adams frequently clashed with Benjamin Franklin over how to manage French relations.
In late 1779, Adams was appointed as the sole minister charged with negotiations to establish a commercial treaty with Britain and end the war.[112] Following the conclusion of the Massachusetts constitutional convention, he departed for France in November,[113] accompanied by his sons John Quincy and 9-year-old Charles.[114] A leak in the ship forced it to land in Ferrol, Spain, and Adams and his party spent six weeks travelling overland until they reached Paris.