[2] His father Giuseppe Antonio Colli (1698–1766) had represented Vigevano with the Habsburg government in Milan and was granted a title of nobility.

[2] Though it was obvious that the First French Republic would invade the Kingdom of Sardinia-Piedmont, King Victor Amadeus III was unable to conclude a defense treaty with Habsburg Austria until 22 September 1792.

Having lost the Duchy of Savoy and County of Nice thanks to the incompetence of his generals, Victor Amadeus asked the Austrians to provide his kingdom with an overall commander.

Meanwhile, Colli was ordered to obey his superior, Charles-François Thaon, Count of Saint-André, but only if de Vins approved.

[6] The Piedmontese defenses in the south were based on a 20 mi (32 km) long line of peaks running from Roquebillière in the west through the Col de Raus, Authion massif, Colle Basse, and Saorge (Saorgio).

[2] In the Second Battle of Saorgio in April 1794, Pierre Jadart Dumerbion's French army turned the eastern flank of the Saorge defenses which were held by Colli and 16,000 Piedmontese soldiers.

The Saorge position was outflanked on its left and attacked in front by the divisions of Jean-Mathieu-Philibert Sérurier and François Macquard.

The next day, the French army under Barthélemy Louis Joseph Schérer attacked to open the Battle of Loano.

Meanwhile, the Austrians in the center and on the left flank were overwhelmed by the French divisions of Massena and Charles-Pierre Augereau, losing 3,500 killed and wounded, 4,000 prisoners, and 48 guns.

[1] Colli was described by his Piedmontese chief of staff C. A. Costa de Beauregard as, "of medium height and very thin; an aquiline nose, a very small graceful mouth, and very lively, big blue eyes, gave him a very remarkable face.

In early 1796, Costa noted that Colli felt that he was in an awkward situation, working for two masters, Austria and Sardinia.

[15] In mid-March 1796, the 70-year-old Johann Peter Beaulieu was promoted Feldzeugmeister and appointed to replace Wallis as commander of the Austrian army in Italy.

[15] The Austrian government gave Beaulieu secret instructions warning him that the Piedmontese might drop out of the war or even change sides.

[19] At the start of the Montenotte campaign, Colli commanded 20,000 Piedmontese troops and 5,000 Austrians in the so-called Auxiliary Corps.

Beaulieu led 32,000 infantry, 5,000 cavalry, and 148 guns, not counting the Auxiliary Corps, but the number of soldiers present for duty was probably less.

The Battle of Millesimo cost the French 700 casualties, but ended when the survivors of the 988 Austrian-Sardinian force surrendered on 14 April.

[24] The French launched a rapid pursuit that overran Colli's defenses and routed his army in the Battle of Mondovì on 21 April.

[26] Historian Martin Boycott-Brown wrote, "If the Austrians had chosen to concentrate closer to the Piedmontese positions, as Colli had wanted, it would have been less easy for Bonaparte to effect their separation".

[14] The Armistice of Cherasco released Colli from his obligations to Victor Amadeus, so he joined Beaulieu's army and was assigned to guard the upper Ticino River with 2 infantry battalions and 2 cavalry squadrons.

Under his command were 2,583 infantry and 80 cavalry under Generalmajor Mathias Rukavina von Boynograd, 518 Austrian Uhlans, and 377 Kingdom of Naples dragoons.