[10] As the peace deteriorated, rumours reached court in September that Protestant cavalry was assembling near Montargis, Catherine instructed Cossé to investigate the matter and report back to her.

[12] With peace established in early 1568 Cossé would be responsible for monitoring the frontier, which many Huguenot nobles were attempting to cross in the wake of Alva's operations in the Spanish Netherlands.

Refugee nobles found much support among the Protestant nobility in Picardy, and attempted to re-enter the Netherlands under arms in July under the captains Mouvans and Cocqueville.

[15] As a man of politique leanings, when informed of the plan to arrest the Huguenot leadership and revoke the Peace of Longjumeau that had ended the second civil war, he was hesitant to enforce the orders.

[16] Once formal civil war had resumed however, he would serve the crown loyally, first assisting with 15 companies of men-at-arms and 2000 footmen in the effort to guard the frontier in Picardy from penetration by Prince of Orange.

[18] He would then move south, fighting alongside the Duke of Montpensier, successfully crushing the viscounts of Quercy and Languedoc when they sought to reach junction with the army under the Prince of Condé in Périgord.

[20] After the destruction of the Protestant army Cossė was among those advocating for the king to seize the moment to gain a favourable peace, the crown was however uninterested, and set about sieging St. Jean-d'Angély in what would prove a costly battle of attrition.

[21] As the siege dragged on with little progress, the king reconsidered the proposal, and Cossé was sent with de Losses to meet with Jeanne d'Albret in La Rochelle to talk terms, however she was uninterested.

[22] In early 1570, Cossé was tasked with seizing the strategic city of La Charité, to deny the Huguenots their primary means of communication across the Loire river.

[23] As Coligny marched on Paris in the final months of the war, Cossé's army would be defeated during their attempt to intercept him at the Battle of Arnay-le-Duc in June.

[28] The attempted assassinations would however slip out of the control of their perpetrators into a general massacre, leaving the politique Cossé in great fear for his life as Catholics considered soft on Protestantism were also targeted.