Foreign affairs 2019 09-10

MICHAEL O’HANLON is a Senior Fellow and Director of Research at the Brookings Institu-

tion’s Foreign Policy Program and the author of The Senkaku Paradox: Risking Great Power

War Over Small Stakes (Brookings Institution Press, 2019), from which this essay is adapted.

September/October 2019 193

Can America Still Protect

Its Allies?

How to Make Deterrence Work

Michael O’Hanlon

S

ince the end o– World War II, U.S. strategic thinking has been

dominated by the doctrine o‘ deterrence. At its most simple, deter-

rence refers to one state’s ability to use threats to convince another

that the costs o‘ some action—say, invading one o‘ its neighbors—will

outweigh the bene¿ts. Such was the logic behind the Cold War concept

o‘ mutual assured destruction: i‘ either the United States or the Soviet

Union used nuclear weapons, the other would respond with nuclear

strikes o‘ its own, resulting in the total devastation o– both. By making

the costs o‘ war intolerably high, both sides hoped to keep the peace.

Yet for Washington, deterrence was never merely about protecting

the U.S. homeland. As it built the postwar system o‘ alliances that today

forms an essential part o‘ the global order, the United States developed

a strategy o‘ “extended deterrence.” According to this strategy, the

United States would use its military power, including its nuclear arsenal,

to defend its treaty allies—among them Japan, South Korea, and the

states o‘ £¬¡¢. The point was not only to discourage Soviet adventurism

in Asia and Europe but also to reassure U.S. allies. I‘ Germany and Ja-

pan (to take just two examples) knew that Washington would guarantee

their security, they would not need to take actions—such as building a

nuclear bomb—that might destabilize the international system.

Today, the Soviet threat is gone, but the strategy o‘ extended deter-

rence remains central to the United States’ global power. Washington

is still, on paper at least, committed to using military (and, i‘ neces-

sary, even nuclear) force to protect its allies from aggression by rivals.

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