Neorealism is a simplified model of international power politics. Sovereign states are the units of the system. The system is characterized by anarchy. That is, the principle of self-help applies to the states: each state acts for itself and there is no institution above the states to enforce agreements. Every state decides independently whether to wage war on another state and states therefore fear each other and try to maximize their own security. The balance of power is formed by the coaction of units. The balance of power is a Nash equilibrium: no state can do better, given what the other states are doing. Moreover, only great powers – states that can put up a fight with the strongest power in the international system – count in the global balance of power.
A traditional domain of realism is alliance formation. This was, of course, very important in the concert of Europe. The system was strongly multipolar and the balance of power was achieved by frequent realignments of great powers. After the Second World War, the international system was bipolar till 1989 and then unipolar after. In a system with only one or two poles there is no room for top-level realignment, which explains why great power alliance formation has not been the subject of much inquiry. But analyzing alliance formation is central to any comparison of theories of international relations.
Faced with a stronger power, states may balance or bandwagon. States balance by increasing their internal efforts or seeking alliances with other powers. Bandwagoning is the preferred option for weak states, especially when they have no hope of balancing and live in the proximity of a stronger power. This is how spheres of influence arise in the international order. Note that the theory of neorealism endeavors to predict alliance formation: which states will form alliances to balance against which state arises endogenously from the theory. Great powers form alliances to balance potential hegemons. For instance, those that formed to check Napoleonic France, Imperial Germany, Nazi Germany, Imperial Japan, and the Soviet Union. Moreover, neorealism tunes out all ideology and cheap talk: what is being balanced is power, not ideological threats.
Stephen Walt has argued for what he calls a balance of threat theory: “Whereas balance of power theory predicts that states will react to imbalances of power, balance of threat theory predicts that when there is an imbalance of threat (i.e., when a state or coalition appears especially dangerous), states will form alliances or increase their internal efforts in order to reduce their vulnerability.”
Furthermore, “Balance of threat theory may appear to be less parsimonious than traditional balance of power theory, because threats are the product of several different components, including the distribution of aggregate power. In fact, the two theories are equally parsimonious; the balance of threat theory is more general and abstract. Whenever one moves to a more general or abstract level of analysis, one inevitably includes more variables. More general theories by definition incorporate a broader range of phenomena. But a more general theory is not less parsimonious, as long as the principal ideas that organize its relevant variables are as few in number as the principal ideas of the less general theory it replaces. The principal concept that informs balance of power theory is power, which consists of components such as military and economic capability and population. The principal concept that informs the balance of threat theory is threat, which consists of aggregate power, proximity, offensive capability, and perceived intentions. Balance of threat theory is a more general explanation of state conduct but not a more complicated one.”
Although quite appealing, this formulation is theoretically problematic. The question comes down to the process of securitization of a given power: which states are seen as threats and which aren’t. This is more or less equivalent to the treatment of securitization in the theory of regional security complexes. Both these theories treat threats as exogenous: one describes the securitization of states in a system first, and then talks about the dynamics of the system. Neorealism, on the other hand, does not require one to specify the internal process of securitization: system structure – how constituent units sit in relations to each other – predicts the securitization of states. Pronouncements of foreign leaders notwithstanding, states fear other states that are more powerful than them. Let’s consider a recent example.
The Obama administration has decided to “rebalance toward the Asia-Pacific region”. One can describe this as a development in the US’ securitization: the United States now sees China as the principal threat to US hegemony. The rebalancing is then seen as containing the Chinese threat. Security analysts and statesmen talk about Chinese authoritarianism, and discuss how to bring China into a rule-based international order where it can be made into a responsible strategic partner. Within the theoretical frame of neorealism, the US move to balance China is an entirely predictable reaction to growing Chinese power.
American, European, and Asian policymakers can talk as much as they like about authoritarianism, democracy, and a rule-based and norm-based international order; neorealism makes a specific prediction. As Chinese power grows, other states will respond to this development by either balancing China, or by bandwagoning with it. One expects strong states in the region – for instance, Japan – and offshore powers to balance China, and China’s weak neighbors – say Burma – to bandwagon.
This makes Obama’s recent visit to Burma especially interesting. The United States is hoping to recruit Burma as a client state. Burma is of great strategic importance to China, being the only possible route to the Indian Ocean not going through the US-controlled Strait of Malacca. China has built a port in Burma and a railroad line to link it to China. If China becomes strong enough to balance the US – and the world becomes bipolar – the US effort to recruit Burma will likely fail, and Burma will end up strictly inside the Chinese sphere of influence. On the other hand, if – as is likely in the medium term – China remains too weak to balance the United States, Burma will become the site of a proxy war if tensions flare up between the US and China.
Of course, when we look at the actual reality of international power politics, we have to describe the securitization of states. But it is crucial to parse the structural factors – which have nothing to do with who is in power and so on – from the contingent factors that impinge on the foreign affairs of states. For instance, Israeli hegemony in the Levant is a structural factor faced by Egyptian policymakers. One may expect the foreign policy of the Muslim Brotherhood to be the polar opposite of President Mubarak, but both have to face the same harsh reality. The requirements of regime stability and domestic control are important, but secondary to structural factors in international security.
You don’t want to know what I think about the role of great men.
 Waltz, Kenneth Neal. Theory of International Politics. Reading, MA: Addison-Wesley Pub., 1979. Print.
 Walt, Stephen M. The Origins of Alliances. Ithaca: Cornell UP, 1987. Print.
 Buzan, Barry, and Ole Wæver. Regions and Powers: The Structure of International Security. Cambridge: Cambridge UP, 2003. Print.