Military bases are commonplace in many countries. Their location has important economic impacts on the neighbouring communities. Their economic impact depends on the level of integration of their activities on the local economies. Base closures or base activity reductions are also frequent as a consequence of military strategy alterations. The current paper seeks to analyse the economic impact of a US base located in the island of Terceira in the Azores. The base has been an important element of economic life in this island since the end of WWII. The changing geosrategical map of the world has, along the second half of the twentieth century, led to changing roles of this base and consequent changes in the intensity of its activity. On the other hand discussions over the importance of the base for the local economy are recurrent in an attempt, on the part of the participants, to set forth arguments in favour or against the presence of military forces in the location. The current paper tries to contribute with a quantification of the economic impact of the base using a dynamic CGE model of the Azorean economy. A closure scenario is created and the impacts raced through various economic indicators including some sector detail. Estimates are made for the overall impact and for the impact on the island that houses the base.