During the Napoleonic Wars he held military commands in the interior and was appointed Baron of the Empire and Grand Officer of the Légion d'honneur.

[2] At the Battle of Kaiserslautern on 28–30 November 1793, he led a brigade in Jean-Jacques Ambert's division in Lazare Hoche's Army of the Moselle.

[1] On 30 April 1794, Jean-Baptiste Jourdan commanding the Army of the Moselle was ordered to send a strong force toward Namur.

[5] Interpreting his orders broadly, Jourdan moved north with the divisions of François Joseph Lefebvre, Jean Étienne Championnet, Antoine Morlot, and Jacques Maurice Hatry, totaling 31,548 effectives, leaving Jean René Moreaux in charge of the remainder of the Army of the Moselle.

The fog lifted, revealing that the Army of the Ardennes soldiers under François Séverin Marceau on the French right flank had fled.

[2] At Fleurus, Jourdan's 75,000 men were attacked by the 52,000-strong Coalition army under Prince Josias of Saxe-Coburg-Saalfeld deployed in five converging columns.

[11] In the Rhine campaign of 1795, Olivier commanded a brigade in Paul Grenier's division in Jourdan's Army of Sambre and Meuse.

[2] On 24 January 1797, Hoche was appointed commander of the Army of Sambre and Meuse which numbered 78,000 men present for duty.

[13] Immediately opposite Hoche's army was Franz von Werneck with 28,841 men including 8,052 soldiers under Paul Kray at Neuwied.

[14] Hoche ordered his left corps under Championnet to move south from Düsseldorf to distract Werneck, then attacked Kray's outnumbered force with 50,000 men.

During the Battle of Neuwied on 18 April, the first assaults of Grenier's corps failed against Kray's line of strong redoubts.

[16] By the secret clauses of the Treaty of Campo Formio, the Holy Roman Empire agreed to cede the Electorate of Mainz to France.

[18][19] While in Étienne Macdonald's Army of Naples, Olivier's division was employed putting down a revolt in Calabria in which the insurgents were defeated.

As the army moved north, discipline broke down and marauding soldiers threatened to kill officers who tried to stop them.

Macdonald accompanied the center column, composed of the divisions of Olivier and François Watrin, which marched from Pistoia to Modena.

[22] On 12 June, the center column attacked Prince Friedrich Franz Xaver of Hohenzollern-Hechingen's 4,000 infantry and 800 cavalry in the Battle of Modena.

[23] After the battle, Macdonald ordered the divisions of Olivier and Joseph Hélie Désiré Perruquet de Montrichard northward in a feint toward the Siege of Mantua.

[25] Macdonald's bold offensive was anticipated by France's enemies; Alexander Suvorov moved the Austro-Russian army by forced marches to oppose him.

The French troops were only halted when Johann I, Prince of Liechtenstein led a cavalry charge against their left flank.

Macdonald decided to retreat that evening, though every Allied attempt to cross to the east bank of the Trebbia had been beaten back.

In August that year he joined the army assembling on the Scheldt and in September he briefly led a National Guard division under Bon-Adrien Jeannot de Moncey.