This chapter demonstrates the continuity and change in, and problematic sources about, Roman rituals, which were linked to the incidence of war and peace. The augurium salutis and the closing of the shrine of Janus Geminus are the two rituals that could only be conducted in time of peace. The burning of enemy arms after a victory was a Roman combat ritual. Another, much rarer, ritual of military return came into renewed prominence under Augustus, namely the dedication of spolia opima, a tradition that was subsequently used to serve the purposes of the Augustan regime. The fetials' rituals were concerned with the preliminaries of war, the solemnization of treaties, and the surrender of Roman offenders. The ritual activities of the fetials addressed the issue of communal responsibility.