The following is the Nov. 5, 2020 Congressional Research Service In Focus report, Defense Primer: Geography, Strategy, and U.S. Force Design.
From the report
World geography is an influence on U.S. strategy, which in turn helps shape the design of U.S. military forces.
World Geography and U.S. Strategy
Most of the world’s people, resources, and economic activity are located not in the Western Hemisphere, but in the other hemisphere, particularly Eurasia. In response to this basic feature of world geography, U.S. policymakers for the last several decades have chosen to pursue, as a key element of U.S. national strategy, a goal of preventing the emergence of regional hegemons in Eurasia. This objective reflects a U.S. perspective on geopolitics and grand strategy developed by U.S. strategists and policymakers during and in the years immediately after World War II that incorporates two key judgments:
- that given the amount of people, resources, and economic activity in Eurasia, a regional hegemon in Eurasia would represent a concentration of power large enough to be able to threaten vital U.S. interests; and
- that Eurasia is not dependably self-regulating in terms of preventing the emergence of regional hegemons, meaning that the countries of Eurasia cannot be counted on to be fully able to prevent, though their own choices and other actions, the emergence of regional hegemons, and may need assistance from one or more countries outside Eurasia to be able to do this dependably.
Preventing the emergence of regional hegemons in Eurasia is sometimes also referred to as preserving a division of power in Eurasia, or as preventing key regions in Eurasia from coming under the domination of a single power, or as preventing the emergence of a spheres-of-influence world, which could be a consequence of the emergence of one or more regional hegemons in Eurasia. The Trump Administration’s December 2017 national security strategy document states that the United States “will compete with all tools of national power to ensure that regions of the world are not dominated by one power.”
Although U.S. policymakers do not often state explicitly in public the goal of preventing the emergence of regional hegemons in Eurasia, U.S. military operations in World War I and World War II, as well as numerous U.S. military wartime and day-to-day operations since World War II, appear to have been carried out in no small part in support of this goal.
U.S. Strategy and Force Design
The goal of preventing the emergence of regional hegemons in Eurasia is a major reason why the U.S. military is structured with force elements that enable it to deploy from the United States, cross broad expanses of ocean and air space, and then conduct sustained, large-scale military operations upon arrival in Eurasia or the waters and airspace surrounding Eurasia. Force elements associated with this objective include, among other things:
- An Air Force with significant numbers of long-range bombers, long-range surveillance aircraft, and aerial refueling tankers.
- A Navy with significant numbers of aircraft carriers, nuclear-powered (as opposed to non-nuclear-powered) attack submarines, large surface combatants, large amphibious ships, and underway replenishment ships.
- Significant numbers of long-range Air Force airlift aircraft and Military Sealift Command sealift ships for transporting ground forces personnel and their equipment and supplies rapidly over long distances.
Consistent with a goal of being able to conduct sustained, large-scale military operations in Eurasia or the oceans and airspace surrounding Eurasia, the United States also stations significant numbers of forces and supplies in forward locations in Europe, the Persian Gulf, and the Indo-Pacific.
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