Which of the following actions might best describe the behavior of a warmonger?

The behavior of a warmonger is characterized by a tendency to promote or provoke conflict, particularly in a manner that suggests a preference for war or military confrontation over peaceful resolutions. This aligns closely with the option of stirring conflict, as a warmonger typically seeks to escalate tensions or encourage hostilities rather than work towards a peaceful solution.

In contrast, encouraging peace, promoting diplomacy, and advocating for cooperation represent behaviors that aim to de-escalate tensions and foster understanding among parties. Warmongers specifically oppose these behaviors, which focus on harmony and resolution through dialogue. Therefore, understanding the essence of a warmonger's behavior as one that intensifies conflict rather than seeks to mitigate it clarifies why the option of stirring conflict is the most fitting description.