The Science of War (Sketch for the ceiling fresco of the first barrel vault in the former court library, today: Austrian National Library, Vienna)

The decline of fresco painting in Venice and north of the Alps following the 30 Years’ War did not last long. The first baroque frescos were painted in Vienna in 1660. After his return from Italy, Gran’s frescos, both sacred and secular, formed the basis of his reputation.
His allegorical ceiling frescos on war and peace (in the National Library, Vienna) according to designs by court scholar Conrad Adolph von Albrecht (1682–1751), are regarded as his main works. They glorify Emperor Charles VI (1685–1740) as commander-in-chief. Prior to executing the frescos, he made preliminary drawings on paper (Monastery of St. Florian collection no. 7) and oil sketches (privately owned). The use of cardboard templates in the original size is indicated by outlines pressed into the plaster, together with references in the documentation of other works. After the outlines had been transferred to the damp plaster, fresco painting could begin, at the rate of 4–6 m2 per day. Strong colours demanded two or three coats of paint.
The Allegory of the Science of War is one of two surviving sketches for the first barrel-vault of the war section. The illusionary effect of the sky zone is enhanced by chiaroscuro painting. The central focus is on Vigilance with the crane, and Hygiene with the staff of Aesculapius, pointing towards Political Wisdom. The flag-bearer and the three putti with commander’s staff, lance and oval shield represent defence. On the left is a rear-view figure with wheel, cog-wheel and spiral stick in his right hand – identifiable, accompanied by the putto with the lifting-jack, as Mechanics. On the right is the muscular Genius of Agriculture with plough and scythe, together with putti bearing fruit, rake and sheaf of corn.

DUCKE Astrid: Gran Daniel, The sience of war, in: DUCKE Astrid, HABERSATTER Thomas, OEHRING Erika: Masterworks. Residenzgalerie Salzburg. Salzburg 2015, p. 96