Aggression can be a fundamental social behavior in many species and is importantly modulated by prior aggressive experience. However, how this experience shapes neural activity and whether it predicts behaviors in novel, more challenging aggression contexts are unknown. Moreover, imitation learning theories of aggression suggest that this behavior can be transferred through observation alone1, but whether this learning leverages the same neural mechanisms as experience is unclear. To address these two questions, here we combine novel behavioral mapping strategies with cell-type-specific and multi-site calcium recordings in a large-scale brain network involved in aggression. We apply these tools in mice “training” in aggression or merely observing this behavior, and later pit these same mice against other aggressors in a “hard” fight context. Using unsupervised behavioral quantification, we find that, in the hard context, while aggressive and observer mice attack at the same level as mice with no experience, the former mice employ a strategy of active defense or aggression readiness absent in the latter. These behavioral differences are further reflected in overlapping patterns of activation in both excitatory and inhibitory neural populations across the hypothalamus, amygdala and forebrain, some of which are conserved from prior training and observation. Moreover, from training to the hard context, aggression experience, and to a lesser extent observation, decrease predictive coding of excitatory population activity in the amygdala and hypothalamus from local and across-region inhibitory populations. Taken together, our findings reveal that aggression experience and observation facilitate a shared strategy of aggression readiness, which is supported by decreased coactivity between excitatory and inhibitory populations at a local and network scale.