During the Battle of Mondovì on 21 April, Guieu's brigade played a prominent role and helped capture the village of Vicoforte.

Surprised by the attack of Peter Ott on 29 July, Guieu rallied 400 men and withdrew to the Palazzo Martinengo in the village of Salò.

[3] Though without food, Guieu withstood a siege by Joseph Ocskay's brigade until the 31st, when Sauret drove the Austrians away after a sharp action.

The presence of a French division so close to the Austrian line of retreat helped Peter Quasdanovich make up his mind to withdraw in the early hours of 4 August.

[5] On the first day of the Battle of Arcola, Bonaparte ordered Guieu to take the 18th and 25th Demi-Brigades across the Adige River at a ferry near Albaredo d'Adige.

In March 1797, he led a division in driving the Austrian army out of northeast Italy, fighting at Sacile and seizing Palmanova.