1. The forerunners: Mengs and Vien (1750-1780)
The discovery of Pompeii in 1748 and the excavations which followed launched a major breakthrough in the history of art as several frescoes were found nearly intact in former Roman houses. Greco-Roman painting had been so far idealized and for the first time painters could directly take their inspiration from genuine Antique paintings.
Two painters were in Rome at this moment, the German Mengs and the Frenchman Vien (as a Prix de Rome recipient). They both created a new style at odds with the prevalent Rococo by drawing straight lines and epurate shapes and colours, and which also recalled the works of Raphael and Poussin (hence the name of Neoclassicism, after the school of the latter). The classical style of the previous century had never totally vanished, thanks to Pompeo Batoni, who besides became the most wanted portraitist in Rome at that time. Mengs was rejoined by his friend Winckelmann, an archaeologist and art historian, who theorized the new style in his History of Ancient Art, written in 1764.
However, the shift with Rococo remained unfinished as Mengs continued to paint the same subjects as the other artists, with just a visual difference. Besides, Mengs later moved to Madrid to work for the Spanish Court where his style was as much appreciated as Tiepolo's. His early death in 1779 also prevented him from going further in copying the Antique.