After training as a musician under the guiding hand of Bologna-born Abbot Bernardo Ottani who also dabbled in painting, Giuseppe Pietro Bagetti learnt the technique of watercolour painting from Pietro Giacomo Palmieri.
On 23 December 1782 the Regia Università di Torino awarded him a degree in civil and military architecture, and it was precisely on coming into contact with the world of military and academic institutions that Bagetti built up his first crucial professional experience, being appointed in 1792 to the post of lecturer in topographical draughtsmanship at the Accademia Militare and Regia Accademia dei Nobili.
In the years immediately thereafter he entered the service of Victor Amadeus III in the Palazzo Reale in a capacity as royal draughtsman of views and landscapes, even following the armies of the House of Savoy when they campaigned against French Republican forces from 1793 to 1796, with a commission to record their feats of arms for posterity. On returning to Turin, he was awarded a lectureship in topography at the Scuola del Genio e il Reale Corpo di Artiglieria in 1797.
In the wake of the French occupation, Bagetti was involved along with other painters in the looting that despoiled the royal palaces of Turin of the works of art that were eventually to swell the collections of the Louvre. In the summer of 1800 Bagetti joined the Piedmontese Topographical Office with the rank of "Captain Engineer Geographer" and was subsequently assigned to the Italian Army, one of his first tasks being to depict the Battle of Marengo – an epic clash that was to spark the legend of Napoleon.
From 1802 to 1805 he travelled around Liguria, the Alpes Maritimes and the Po Valley, drawing views of the chief battles fought by the French Army in the course of its first campaign in Italy; subsequently, he followed the Northern Army in Germany, and took part
in the Campagne de Russie, producing graphic documentation recording the most important military operations conducted on those fronts.
He moved to Paris in 1806, and between 1806 and 1807 he produced a second series of views of the former Republic of Venice. In 1807 Napoleon ordered that the entire series of his 68 watercolours be displayed in the Gallery of the Château de Fontainebleau, and in 1811 he decorated the painter with the Légion d'Honneur for producing a bird's-eye-view map of Italy from the Alps to Naples.
In 1812 Bagetti showed his work at the Salon in Paris, winning a gold medal. Returning to Turin after the emperor's defeat in 1815, he taught topography at the Accademia Militare and watercolour painting at the Accademia di Belle Arti. His sketches in the field served as a basis for a series of watercolours and tempera works.
In c. 1830, under the guidance of General Pelet, the director of the French War Department, work began on engraving Bagetti's works for use in a catalogue entitled Vues des champs de bataille. Bagetti died in Turin on 29 April 1831, and in 1834 Louis-Philippe of France had the 68 watercolours moved to Versailles, where the château was being transformed into the Musée de l'Histoire de France.