Realism and World Politics

to dominate the continent and thereby pose a threat to the physical security

of the British Isles. After the Second World War, Western Europe was com-

pelled to ally itself with the United States because of the size and geographical

propinquity of the Soviet Union.^10

There has not been great variation over time in the general pattern of power
distribution in the international system. The sovereign state system was multi-polar

• always with five or more great powers – until 1945. It was bipolar during the Cold
  War. With the demise of the Soviet Union, most structural realists tend to see the
  system as unipolar – with the United States as the single preponderant power.^11
  Unipolarity is a difficult situation for structural realism, especially as regards the
  leading power. That is because the United States is sufficiently powerful so as to be
  unconstrained by the international system: the ‘pressures of competition’ are absent;
  no other state, or combination of states, can mount a serious threat against the
  survival and autonomy of the United States. In other words, the master explanatory
  variable of systemic competition explains very little in a situation of unipolarity.
  What structural realism does suggest is that a unipolar state may be tempted to
  do either too much or too little. On the one hand, it can embark on ambitious
  expansionist policies, making its influence felt everywhere; on the other hand, it
  may become introvert and isolationist, preoccupied with its own domestic agenda.
  Any combination of those extremes is of course also possible. But whatever the
  unipolar power chooses to do, structural realism cannot offer an explanation for it:

in the absence of systemic constraints, states may follow a wide range of

policies. The most likely explanation for the policies followed by a particular

state would be the values embodied in the domestic political order, although

other interpretations, such as the interests of particular bureaucracies or the

unconscious psychological drive of specific leaders, might be equally

compelling.^12

Structural realism helps us understand why all these factors become relevant in the
absence of serious systemic constraint; but the theory offers little help in under-
standing concrete policy choices: it is not a theory of foreign policy.
The twists and turns of a unipolar foreign posture was amply demonstrated by
the administration of George W. Bush. The 9/11 attacks led to a global war on
terrorism which was defined as the ‘Long War’ and was explicitly compared to the
Cold War as ‘a similar sort of zero-sum, global-scale generational struggle against
anti-liberal ideological extremists who want to rule the world’^13. Most structural
realists remain sceptical about the war on terror, because they consider the terrorist
threat ‘pretty small beer’.^14 As it turned out, the invasion of Iraq could not be
justified by Saddam Hussein’s possession of weapons of mass destruction; nor was it
possible to demonstrate a connection between Saddam and international terrorism.
Many structural realists think of the invasion as an ‘Unnecessary War’;^15 supporters
of the administration, of course, claimed that it was doing exactly the right thing.^16

Structural realism and changes in statehood 109