After the revolution of 1789 he took part in the campaigns of the revolutionary French armies, during the War of the First Coalition, in 1793 as a captain in the Légion franche étrangère (Free foreign legion), where he led the 1st company chasseurs à pied.

[2] Chassé's battalion formed the vanguard of Daendel's attack on the Bommelerwaard and the capture of Zaltbommel, shortly before the fall of the Dutch Republic in January 1795.

[3] He usually performed garrison duties, but was with his Jagers in 1799 part of the Franco-Batavian army that countered the Anglo-Russian invasion of Holland.

[2] King Louis Bonaparte put him in command of the Dutch brigade (part of the Division-Leval) that his brother Napoleon obliged him to contribute to the French campaign in Spain in 1808.

For his exploits in that harsh guerilla war in the battles of Zornoza, Mesas de Ibor (1809), Talavera (1809), Almonacid (1809) and Ocana (1809; where he assumed command of the Division-Leval),[4] King Louis created Chassé baron on 1 July 1810, just one week before Napoleon annexed the Kingdom of Holland to the French Empire.

Like many Dutchmen, Chassé resented this annexation, so much so, that he refused to accept the diplome in which Napoleon elevated him to baron de l'Empire on 30 June 1811.

[4] At the battle of Waterloo Chassé's third division was part of the First Netherlands Corps under the Prince of Orange in the right-center of the Duke of Wellington's Anglo-Allied army.

As Wellington, who had often fought against Chassé in Spain, was still apprehensive about his military skill,[c] the third division was placed in and around the town of Braine l'Alleud, behind the right wing.

In response he ordered Major Van der Smissen to send the Horse artillery battery commanded by Captain Carel Frederik Krahmer de Bichin into the firing line.

In preparation for the second counterattack Chassé ordered the Detmers brigade (part of the division) to take position behind Van der Smissen.

[d] His counterattack was to be a bayonet charge, as Chassé had a predilection for this type of manoeuvre (that had earned him the nickname of "général baionette" from Napoleon), and it proved to be decisive.

After the beginning of the Belgian Revolution he replaced Prince Frederick of the Netherlands as commander-in-chief of Dutch forces in Belgium on 17 October 1830.

In 1832 (by now a full general) he commanded a garrison of 5,000 Dutch troops that was besieged by a French army under Marshal Gérard ten times that number.

[5] This earned him a knight's-grand cross in the Military William Order by promotion, and the admiration of the French, who made his imprisonment in Saint-Omer as pleasant as feasible.