Abel Servien, Count of la Roche des Aubiers, was the most important French delegate to the Congress of Westphalia. He had been Minister of War in the early 1630’s but was sacked in 1636 when France’s first year of open war against the Habsburgs turned out disastrously. He was brought back into public service by his friend Cardinal Mazarin, with whom he had negotiated the Peace of Cherasco in 1631 (Mazarin as papal mediator, Servien representing France), and appointed as a plenipotentiary to Westphalia in place of the vacillating Count of Chavigny.
Servien’s time in Westphalia was marred by ongoing quarrels with his colleague, the Count d’Avaux, who was higher in rank but not as close to Mazarin politically. The two blamed each other for problems in the negotiations and even at times wrote pamphlets attacking each other. The arrival of the Duke of Longueville kept the feud under wraps, but when Longueville was granted permission to retire in early 1648, Servien quickly maneuvered to have d’Avaux recalled. Servien was in a stronger political position vis-à-vis d’Avaux because of his close relationship with Mazarin, and also because his nephew, Hugues de Lionne, was Mazarin’s secretary and kept Servien informed of affairs at court.
Servien supported Mazarin’s policy of aggressive negotiation for territorial gain at the expense of consensus. Like Mazarin, he misunderstood the Dutch desire for peace, and was unable to convince them to stay in the war during a six-month sojourn in The Hague at the beginning of 1647. Nevertheless, his firm line with the Austrian Habsburgs led to the acquisition of Alsace, and Servien was the only French plenipotentiary to sign the peace in October 1648.
Louis XIV and Abel de Servien (2012) by Louis-Marc Servien: Few representatives have a monograph devoted to them, and to have one in English is still rarer. I have not had a chance to view this work, as it appears the only copies are in Europe.