Having an incident response retainer, or even a pre-approved external incident response firm, is not the same as being ready for an incident. A retainer means someone will answer the phone. Operational readiness determines whether that team can do meaningful work the moment they do. That distinction matters far more than many organizations realize. In the first hours of a security incident, attackers are not waiting for your identity team to provision emergency accounts, for legal to decide whether an outside firm can access sensitive systems, or for someone to figure out who owns the EDR console. Every delay gives the attacker more uninterrupted time in your environment. Every hour lost to logistics increases the likelihood of deeper compromise, broader impact, and more expensive recovery. The same is true internally. An organization may have an incident response plan, a capable security team, and a list of escalation contacts, yet still be unprepared to respond under pressure. Readiness is not measured by what exists on paper. It is measured by how quickly responders, internal or external, can gain visibility, understand what the attacker has already touched, and make informed decisions. On Day Zero, responders are not asking for unlimited control. They are asking for visibility first and authority second. Without visibility, containment decisions are made blindly, timelines cannot be reconstructed, and the true scope of the compromise remains unknown while the response team debates access and approvals. This guide outlines what responders need on Day Zero, where organizations most often fall short, and how to ensure your internal team and external IR partner can begin effective work immediately when an incident is declared. Whether the first responders are internal security staff, an external retainer firm, or both working in parallel, they need access to the same core systems. Internal teams may already have some of that access. External responders usually