After commanding a brigade with distinction during the War of the Fifth Coalition at Aspern-Essling and Wagram he was promoted and made chief of staff to Marshal André Masséna.

On 25 August he and French naval Captain Montcabrié attacked the fortified island of Dänholm between Stralsund and Rügen.

The 1,200-man French force included one battalion of the 30th Light Infantry Regiment, two artillery pieces and crews, and detachments of sappers, miners, and Sailors of the Imperial Guard.

[7] At the Battle of Aspern-Essling, Boudet's division heroically defended Essling for the better part of two days against repeated Austrian attacks.

[8] During the struggle, Marshal Jean Lannes wrote out a special commendation for Fririon's valiant fighting, "General, you have covered yourself with glory, you and your brigade; I will report your conduct to the Emperor".

[10] On the second day, the VI Austrian Corps fell on Boudet's isolated division, overwhelming it and capturing its artillery.

[2] He soon became chief of staff to Marshal Masséna, replacing Nicolas Léonard Beker who had angered Emperor Napoleon.

[13] At the Siege of Almeida, Fririon carried an ultimatum to William Cox, the fortress commanding officer, after the fort's main magazine exploded,[14] killing 600 defenders.

[16] The night before, Fririon recommended that the Anglo-Portuguese army of Arthur Wellesley, Viscount Wellington be flanked out of position instead of assaulted directly.

Masséna dismissed this idea, saying, "You are of the Army of the Rhine, you like to maneuver; this is the first time that Wellington appears disposed to offer battle.

[16] While the French army was before the Lines of Torres Vedras, Fririon urged that the VIII Corps be withdrawn from its exposed position at the village of Sobral.

However, Masséna appeared to rely too much on his senior aide-de-camp, Jean-Jacques Germain Pelet-Clozeau and sometimes changed his instructions without consulting with Fririon.

Did no one reflect that, by deceiving them in this way, the government made enemies of all those who trusted for a time in the exactitude of the Bulletins, and lost their illusion soon after, when they learnt the melancholy ends of their sons and brothers?