This document discusses how geographic information systems (GIS) can be used to manage military installations and critical infrastructure. GIS is used for land and facility management, including range management, emergency planning, force protection, security, base operations, environmental management, and building management. It allows managing entire defence estates on a national scale down to the room and equipment level. GIS also supports enterprise facility management, emergency preparedness and response, environmental management, and infrastructure asset management. When applied to defence installation management, GIS follows patterns like those in service-oriented architectures and can integrate various systems and applications. It extends facilities management to support antiterrorism/force protection by assessing vulnerabilities, critical assets, utilities, and performing blast modeling, sensor