Pierre Duhem is an unavoidable figure if one wants to scrutinize the progress in the mixed science of mechanics and thermodynamics in the period 1880–1920. He is a prolific writer and a never tired propagandist of the global science of energetics. Here we examine his main contribution, its novelty and its inherent limitations in the light of two remarkable synthetic and/or critical works, his treatise on energetics (Traité d’énergétique ou de thermodynamique générale. Gauthier-Villars, Paris, 528+504 pages, 1911) and his series of papers (Duhem in L’évolution de la mécanique. A. Joanin, Paris, 1903) on the “Evolution of Mechanics” (of which we also provide a partial translation). These works are replaced in their socio-scientific background with its main sources (Gibbs and Helmholtz) and its possible interaction with, and influence on, contemporary scientists. A particular emphasis is put on Duhem’s style and interests that are strongly influenced by his combined epistemological, philosophical and historical vision. We concentrate on the specialized fields examined and tentatively improved by Duhem in the “Evolution of mechanics”, with a personal interest in those “nonsensical branches”—friction, false equilibria, permanent alterations, hysteresis—that Duhem tries to attach to the former Gibbs’ statics and Helmholtz’ dynamics by way of subtle generalizations. In this analysis we account for the enlightening comments of contemporaries (E. Picard, J. Hadamard, O. Manville), of his various biographs, and of Duhem’s own perusal (Duhem in Notice sur les titres et travaux de Pierre Duhem, 1913) of his oeuvre. We conclude with modern developments which provide answers to queries of Duhem that now appear as too much in advance on their time.