The ideology of Mission Assurance was borne out of the U.S. Air Force’s need to ensure the continued function and resilience of capabilities and assets critical to the execution of Defence mission-essential functions. Applying this mentality to cyber security operations changes the perspective through which defensive cyber activities are perceived, planned, and executed. Temporal context, business criticality, and service to mission overlays increase the complexity of cyber defence challenges, transforming security ventures away from system-oriented approaches to mission-oriented ones. Lessons from this military concept have significant consequences outside of the defence context. Assurance of government assets, national critical infrastructure, financial sectors and healthcare are all areas where Mission Assurance principles can be applied to minimise the cost of service-wide outages and cascading failure. This presentation will exemplify a fictional Intelligent Transport System incident response scenario to demonstrate how the application of Mission Assurance principles minimise service degradation compared to traditional cyber incident response methods. It will address this conceptually, then elaborate technically through the consideration of specific tactical courses of action to deliver technical mitigation procedures against the intrusion set.