Defense-related extensions include Esri Defense Mapping, for producing and maintaining high-quality topographic databases and cartographic products, and the Grid Manager, for creating specialized grids, graticules, and borders.
Other extensions used with ArcGIS 10 for Defense and Intelligence Analysis include Spatial Analyst, 3D Analyst, and Tracking Analyst.
For ArcGIS 9.3.1 military users, we recommend that you download the ArcGIS Military Analyst and Military Overlay Editor extensions. These extensions are not necessary if you are using ArcGIS 10.