Public negotiation announcements signal weakness and embolden insurgents. [causal]
In advance of his departure he addressed to the government an important and prophetic "testament", warning it of three main dangers ahead. First, he feared lest the morale of the army might break: "disquiet, discouragement and disgust among the military is at its peak, especially in the lower echelons, that is to say those who get themselves killed feeling that France has no gratitude for them". Secondly, there was the danger of announcing publicly an intention to negotiate with the rebels; this would "suffice to convince the population once and for all that the rebels are winning and to induce it, for fear of reprisals, to take refuge in the camp of the victors". Thirdly, it would be disastrous to attempt to negotiate a settlement through an ad hoc Algerian Assembly acting as an interlocuteur valable because rebel terror would swiftly reduce such a body to subservience, and it would then inevitably opt for secession from France.
XREF: Connects to counterinsurgency doctrine and propaganda theory about the signaling effects of peace overtures.
Horne, Alistair, A Savage War of Peace- Alge…, loc. 397