In a military context, the collection, analysis, and use of geographic data can provide leaders with timely and accurate information on which to base decisions. GIS systems are used to store, manipulate, analyze, and manage all types of geodata, and are widely used by many military organizations in military decision making processes (MDMPs). Apart from accuracy, usage of GIS in MDMPs has provided many advantages, becoming a powerful and popular tool in the militaries of developed countries. However, even though GIS is a sophisticated tool in MDMP, the Sri Lankan Army has not employed widespread use of these systems. Tactical operations in which covert movement is paramount to success depend on high quality data and information concerning enemy positions, as was the case in the Sri Lankan Civil War (1983-2009). A case study of base siting using GIS is explored here; in this research we attempt to introduce GIS as a powerful tool in MDMPs in the Sri Lankan military. Sri Lanka is a developing country that suffered from a terrorist war for more than 30 years. All decision making and data gathering was done manually, spending more money and man power that was realistically necessary. This research is focused on providing solid evidence for the use of GIS techniques in MDMPs, which can partially supplant slower, less reliable humanbased decision making processes. In selecting a suitable permanent or temporary military operation base in enemy territory, all parameters need to be evaluated accurately. Injecting logical and statistical data, thus more automated processes into command-level decisions, will minimize errors in MDMPs. The analytic hierarchy process (AHP) is utilized to structure commander’s perceptions of important selection criteria, and optimal base selection procedures are described.