This Environmental Impact Statement (EIS) is prepared in accordance with Air Force regulations, the National Environmental Policy Act (NEPA), and the President's Council on Environmental Quality (CEQ) guidelines to assess the combined impacts of the Mountain Home Air Force Base (MHAFB) realignment and a proposed expanded range capability. This EIS is the beginning or Tier 1 of an environmental analysis process that addresses the specific impacts to MHAFB and its environs. This Tier 1 EIS, in addition to evaluating the specific impacts of the MHAFB realignment actions, identifies and evaluates in general terms the potential expansion of range capability in southwestern Idaho and any reasonable alternatives available to meet training requirements. Air Force short-term, intermediate, and long-term training requirements are also identified in this Tier 1 EIS. Tier 1 will contribute to the decision to either proceed further with detailed studies and analysis for a range capability expansion in southwestern Idaho, or to select other alternatives. This Tier 1 EIS provides the initial framework (operational requirements, range development criteria, environmental attributes for the area, and description of environmental impacts associated with ranges) for use in a subsequent Tier 2 EIS if the decision is made to pursue a range expansion option. (sdw).