Defense Primer: Geography, Strategy, and U.S. Force Design

Defense Primer: Geography, Strategy, and U.S. Force Design

Defense Primer: Geography, Strategy, and U.S. Force Design

Updated December 8, 2025 (IF10485)

World Geography and U.S. Strategy

World geography is an influence on U.S. strategy, which in turn helps shape the design of U.S. military forces. 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 beginning in the 1940s chose to pursue, as a key element of U.S. national strategy, a goal of preventing the emergence of regional hegemons in Eurasia. This goal reflected a U.S. perspective on geopolitics and grand strategy that incorporated two key judgments: (1) 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 (2) 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, through their own choices and 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 has also sometimes been 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. Although U.S. policymakers may not always publicly state 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 in subsequent years, appear to have been carried out in no small part in support of this goal.

The goal of preventing the emergence of regional hegemons in Eurasia is a major reason why the U.S. military has been 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. These include, among other things, (1) an Air Force with significant numbers of long-range bombers, long-range surveillance aircraft, and aerial refueling tankers, (2) 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, (3) 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, and (4) significant numbers of forces and supplies in forward locations in Europe, the Indo-Pacific, and the Persian Gulf.

Comparing U.S. Forces to Other Countries' Forces

The United States is the only country in the world that has designed its military to be able to depart one hemisphere, cross broad expanses of ocean and air space, and then conduct sustained, large-scale military operations upon arrival in another hemisphere. The other countries in the Western Hemisphere have not designed their forces to do this because they cannot afford to, and because the United States, in effect, has been doing it for them. Countries in the other hemisphere do not design their forces to do this for the very basic reason that they are already in the other hemisphere, and consequently instead spend their defense money primarily on forces that are tailored largely for influencing events in their own local regions of that hemisphere. (Some countries, such as Russia, China, the United Kingdom, and France, have an ability to deploy forces to distant locations on a much smaller scale.)

The fact that the United States has designed its military to do something that other countries have not designed their forces to do can be important to keep in mind when comparing the U.S. military to the militaries of other nations. For example, the U.S. Navy has 11 aircraft carriers while other countries generally have no more than one or two. (China has three and is expected by some observers to eventually have a total of six or more.) Other countries do not need a significant number of aircraft carriers because, unlike the United States, they are not designing their forces to cross broad expanses of ocean and air space and then conduct sustained, large-scale military aircraft operations upon arrival in distant locations. As another example, it is sometimes noted that U.S. naval forces are equal in tonnage to the next several navies combined, and that most of those several navies are the navies of U.S. allies. Those other fleets, however, are mostly of Eurasian countries. The fact that the U.S. Navy is much bigger than allied navies reflects the differing and generally more limited needs that U.S. allies have for naval forces. (It might also reflect an underinvestment by some of those allies to meet even their more limited naval needs.)

The United States has needs for military forces that are quite different from the needs of countries that are located in Eurasia. The sufficiency of U.S. military forces consequently is best assessed not through comparison to the militaries of other countries (something that is done quite frequently), but against U.S. strategic goals.

Regional Differences and Force Design

The geography of Eurasia itself is a factor in U.S. force design. Eurasia includes three regions that since the 1940s have been of particular interest to U.S. policymakers and military force planners—East Asia (where potential adversaries have included China and North Korea), Southwest Asia (which has included potential adversaries such as Iran), and Europe (where the potential adversary has been the Russia [and before that, the Soviet Union]). For the U.S. military, the Indo-Pacific is generally viewed as more of a maritime and aerospace theater of operations, meaning a theater where naval forces (i.e., the Navy and Marine Corps) and the Air Force are more predominant, while Europe is generally viewed as more of a continental or land-oriented theater of operations, meaning a theater where the Army and the Air Force are more predominant. A choice by U.S. policymakers to put more emphasis on one of these theaters than the other can thus affect the composition of U.S. military forces.

Force-Planning Standard

The term force-planning standard refers to the number and types of simultaneous or overlapping conflicts or other contingencies that the U.S. military should be sized to be able to conduct—a planning factor that can strongly impact the size of the U.S. defense budget. (Other terms for referring to the force-planning standard use force-sizing instead of force-planning, and construct or metric instead of standard.) Following the end of the Cold War, U.S. military forces were sized to be able to fight and win two overlapping major regional conflicts or major regional contingencies (MRCs). In subsequent years, the U.S. force-planning standard was altered to what was referred to as a win-hold standard, meaning an ability to fight and win one MRC while conducting a holding action in a second MRC. Subsequent to that, it was modified to one of fighting and winning one major conflict while also conducting certain smaller-scale operations. The reemergence of great power competition with China and Russia over the past 10 to 15 has prompted some observers to recommend that the force-planning standard should be changed to one of being able to fight two simultaneous or overlapping major conflicts—a so-called two-war or two-major-war standard—or some other construct for engaging in multiple simultaneous or overlapping major conflicts.

2025 National Security Strategy

The Trump Administration's 2025 national security strategy document (see box below), released on December 4, 2025, states that "[s]topping regional conflicts before they spiral into global wars that drag down whole continents" is a priority, and that the United States "cannot allow any nation to become so dominant that it could threaten our interests" and will "work with allies and partners to maintain global and regional balances of power to prevent the emergence of dominant adversaries." The document states that the United States "expect[s] our allies to spend far more of their national Gross Domestic Product (GDP) on their own defense…."

The document places an emphasis on defense of the U.S. homeland and U.S. preeminence in the Western Hemisphere. It states that the United States "must reconsider our military presence in the Western Hemisphere," to include a "readjustment of our global military presence to address urgent threats in our Hemisphere ... and away from theaters whose relative import to American national security has declined in recent decades or years."

The document also places an emphasis on countering China and deterring potential conflict in the Indo-Pacific. It states that the United States will "[work] to align the actions of our allies and partners with our joint interest in preventing domination by any single competitor nation" in the Indo-Pacific; that "deterring a conflict over Taiwan, ideally by preserving military overmatch, is a priority"; and that the United States "will build a military capable of denying aggression anywhere in the First Island Chain. But the American military cannot, and should not have to, do this alone. Our allies must step up and spend—and more importantly do—much more for collective defense."

The document's section on Europe states that U.S. policy for the region should prioritize, among other things, "[e]nabling Europe to stand on its own feet and operate as a group of aligned sovereign nations, including by taking primary responsibility for its own defense, without being dominated by any adversarial power." The document's section on the Middle East states that some of the reasons why the region historically has been a high U.S. regional priority "no longer hold," that "[c]onflict remains the Middle East's most troublesome dynamic, but there is today less to this problem than headlines might lead one to believe," and that "[i]nstead, the region will increasingly become a source and destination of international investment."

Strategy Is a Policy Choice, Force Design Is a Consequence

A change in U.S. foreign policy, U.S. role in the world, and U.S. grand strategy (including regional prioritization) could lead to a change in the U.S. force-planning standard, the size and composition of U.S. military forces, and U.S. defense plans, programs, and budgets. That U.S. policymakers starting in the 1940s chose to pursue a goal of preventing the emergence of regional hegemons in Eurasia does not necessarily mean this goal was a correct one for the United States to pursue, or that it would be a correct one for the United States to pursue in the future. Whether it would be a correct one for the United States to pursue in the future would depend on policymaker views regarding the two key judgments outlined earlier. A decision on whether to continue pursuing such a goal would then influence U.S. military force design for the future.

CRS Products

CRS Report R43838, Great Power Competition: Implications for Defense—Issues for Congress, by Ronald O'Rourke.

Other Resources

White House, National Security Strategy of the United States of America, November 2025 (released December 4, 2025), 29 pp.