Power and the Varieties of Order - Liberal Leviathan: The Origins, Crisis, and Transformation of the American World Order - page 31

idly expanded its defense budget after 2001. As a result, the United States today spends on
defense approximately as much as the rest of the world combined. In 2009, America's share
of world defense expenditures was approximately 43 percent, and it was about 64 percent of
defense expenditures by the great powers. (See table 2-2 .)
Table 2-1
Great Power GNI, 1986-2008 a
Table 2-2
Great Power Defense Expenditures 2009
These combined economic, military, and technological advantages give the United States
“command of the commons.” Barry Posen argues that it is the ability of a leading state to mil-
itarily dominate the global commons—that is, mastery of sea and space areas—that provides
the defining feature of unipolar military power. He notes that it is this mastery of the global
commons that is the key to American global power:
Command of the commons is the key military enabler of the U.S. global power posi-
tion. It allows the United States to exploit more fully other sources of power, including
its own economic and military might as well as the economic and military might of its
allies. Command of the commons also helps the United States to weaken its adversar-
ies, by restricting their access to economic, military and political assistance. . . . Com-
mand of the commons provides the United States with more useful military potential
for a hegemonic foreign policy than any other offshore power has ever had. 12
What is clear is that power distributions—and the concentration of power in the hands of a
leading state—vary widely across the last centuries, and from this comparative-historical per-
spective, the current system is uniquely unipolar. What is remarkable about American power
is that it has been so durable and multifaceted. The United States has accounted for roughly a