In 1578, the king's long serving captain of the Scots Guard died, and Henri chose Châteauvieux for the prestigious post.

The following year, Henri decided that he could no longer tolerate the humiliations imposed upon him by the Catholic ligue and resolved to assassinate its leader the duke of Guise.

Châteauvieux, as captain of the guard had a part to play in this plan, stationing his soldiers outside the residence of the duke's mother Anne d'Este keeping her under watch.

In 1601 he was created comte de Confolant and granted the office of bailli of several recently conquered territories from Savoie.

His father had served previous kings of France, occupying the offices of maître de l'hôtel du roi, commander of the Swiss of Valais and bailli of Bresse.

[6] Ultimately the siege would be brought to a negotiated conclusion, Anjou keen to depart after word arrived that he had been elected as king of the Polish-Lithuanian Commonwealth.

[7] Châteauvieux travelled with Anjou to the Commonwealth, serving him as a gentilhomme de la chambre during his tenure in the country.

72 members were inducted into this confraternity, among them Épernon and his brother La Valette, Marshal Retz and all the captains of Henri's guard among them Châteauvieux.

[20] Having been excluded from re-entering the council chamber back to their master after having been called away, it became clear to Guise's secretary Péricard, that the duke was in danger.

He next attempted to reach the duke's mother the duchesse de Nemours, however her residence was guarded by Clermont d'Entragues and Châteauvieux, both of whom had been ordered by the king to station their Swiss on the door and allow no one to enter or leave.

[21] Péricard was right to be concerned, shortly thereafter the duke would be called from the council into a side chamber, where he would be cut down by members of the king's bodyguard, the Quatre Cinq.

Several of Henri's favourites: Clermont d'Entragues, D'O and Châteauvieux were all scandalised by this behaviour from their lord, meanwhile Marshal D'Aumont took the opinion that only 'homosexuals' would object to this olive branch to the Protestants.

[26] On 1 August while preparing to begin the siege of Paris, Henri was fatally wounded by the radical Catholic Jacques Clément.

Henri was not insensitive to these dispositions, and was aware that service to him had the potential to violate their religion and also impede their access to favour, given he already had a household of his own.

[27] To this end after some confusion, Henri would issue a declaration on 4 August by which he promised to protect the Catholic religion and host a general council to resolve the religious question.

[28] Among those who signed this declaration by Henri would be the duc de Longueville, the lieutenant-general of Champagne Dinteville, Marshals D'Aumont and Biron, and the captains of the guard Clermont-D'Entragues, Manou and Châteauvieux.

He was also granted the position of bailli for territories won for France in the recent war with Savoie: Bresse, Bugey, Valromey.

This change was a response to an incident in which Henri IV had taken off during a hunt escaping from his guards protection to spend some time in an inn with merchants.