Offensive Realism in Brief
John Mearsheimer
OFFENSIVE REALISM IN BRIEF

In its simplest form, my theory maintains that the basic structure of the international system forces states concerned about their security to compete with each other for power. The ultimate goal of every great power is to maximize its share of world power and eventually dominate the system. In practical terms, this means that the most powerful states seek to establish hegemony in their region of the world while also ensuring that no rival great power dominates another area.

The theory begins with five assumptions about the world, which are all reasonable approximations of reality. First of all, states are the key actors in international politics, and no higher authority stands above them. There is no ultimate arbiter or leviathan in the system that states can turn to if they get into trouble and need help. This is called an anarchic system, as opposed to a hierarchic one.

The next two assumptions deal with capabilities and intentions, respectively. All states have offensive military capabilities, although some have more than others, indeed sometimes many more than others. Capabilities are reasonably easy to measure because they are largely composed of material objects that can be seen, assessed, and counted.

Intentions are a different matter. States can never be certain about the intentions of other states, because intentions are inside the heads of leaders and thus virtually impossible to see and difficult to measure. In particular, states can never know with complete confidence whether another state might have its gun sights on them for one reason or another. The problem of discerning states’ intentions is especially acute when one ponders their future intentions, since it is almost impossible to know who the leaders of any country will be five or more years from now, much less what they will think about foreign policy.

The theory also assumes that states rank survival as their most important goal. This is not to say it is their only goal, for states invariably have numerous ambitions. However, when push comes to shove, survival trumps all other goals, basically because if a state does not survive, it cannot pursue those other goals. Survival means more than merely maintaining a state’s territorial integrity, although that goal is of fundamental importance; it also means preserving the autonomy of a state’s policymaking process. Finally, states are assumed to be rational actors, which is to say they are reasonably effective at designing strategies that maximize their chances of survival.

These assumptions, when combined, cause states to behave in particular ways. Specifically, in a world where there is some chance—even just a small one—that other states might have malign intentions as well as formidable offensive military capabilities, states tend to fear each other. That fear is compounded by what I call the “9-1-1” problem—the fact that there is no night watchman in an anarchic system whom states can call if trouble comes knocking at their door. Accordingly, they recognize they must look out for their own survival, and the best way to do that is to be especially powerful.

The logic here is straightforward: the more powerful a state is relative to its competitors, the less likely its survival will be at risk. No country in the Western Hemisphere, for example, would dare attack the United States, because it is so much stronger than any of its neighbors. This reasoning drives great powers to look for opportunities to move the balance of power in their favor, as well as to prevent other states from gaining power at their expense. The ultimate aim is to be the hegemon: that is, the only great power in the system.

When people talk about hegemony today, they are usually referring to the United States, which is often described as a global hegemon. However, I do not believe it is possible for any country—including the United States—to achieve global hegemony. One obstacle to world domination is that it is very difficult to conquer and subdue distant great powers, because of the problems associated with projecting and sustaining power over huge distances, especially across enormous bodies of water like the Atlantic and Pacific Oceans. This problem is less acute when dealing with minor powers, but even so, the power of nationalism makes it extremely difficult to occupy and rule a hostile country. The paramount goal a great power can attain is regional hegemony, which means dominating one’s surrounding neighborhood. The United States, for example, is a regional hegemon in the Western Hemisphere. Although it is plainly the most powerful state on the planet by far, it is not a global hegemon.

Once a state achieves regional hegemony, it has a further aim: to prevent other great powers from dominating their geographical regions. In other words, no regional hegemon wants a peer competitor. The main reason is that regional hegemons—because they are so dominant in their neighborhood—are free to roam around the globe and interfere in other regions of the world. This situation implies that regional hegemons are likely to try to cause trouble in each other’s backyard. Thus, any state that achieves regional hegemony will want to make sure that no other great power achieves a similar position, freeing that counterpart to roam into its neighborhood.

Most Americans never think about it, but one of the main reasons the United States is able to station military forces all around the globe and intrude in the politics of virtually every region is that it faces no serious threats in the Western Hemisphere. If the United States had dangerous foes in its own backyard, it would be much less capable of roaming into distant regions.
But if a rival state achieves regional dominance, the goal will be to end its hegemony as expeditiously as possible. The reason is simple: it is much more propitious to have two or more great powers in all the other key areas of the world, so that the great powers there will have to worry about each other and thus be less able to interfere in the distant hegemon’s own backyard. In sum, the best way to survive in international anarchy is to be the sole regional hegemon.
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