Deterrence isn't what it used to be. In the second half of the twentieth century, it was the backbone of U.S. national security. Its purpose, logic, and effectiveness were well understood. It was the essential military strategy behind containing the Soviet Union and a crucial ingredient in winning the Cold War without fighting World War III. But in recent decades, deterrence has gone astray, and U.S. defense policy is worse for the change.
Since the Cold War ended, the United States has clung to deterrence where it should not have, needlessly aggravating relations with Russia. More important, it has rejected deterrence where it should have embraced it, leading to one unnecessary and disastrous war with Iraq and the risk of another with Iran. And most important, with regard to China, Washington is torn about whether or not to rely on deterrence at all, even though such confusion could lead to a crisis and a dangerous miscalculation in Beijing.
Mistakes in applying deterrence have come from misunderstandings about the concept itself, faulty threat assessments, forgetfulness about history, and shortsighted policymaking. Bringing these problems into focus can restore faith in deterrence where it has been lost, lower costs where the strategy has been misapplied, and reduce the danger of surprise in situations where the risk of conflict is unclear.
Deterrence is a strategy for combining two competing goals: countering an enemy and avoiding war. Academics have explored countless variations on that theme, but the basic concept is quite simple: an enemy will not strike if it knows the defender can defeat the attack or can inflict unacceptable damage in retaliation.
At best, applying deterrence when it is unneeded wastes resources. At worst, it may provoke conflict rather than hold it in check. And even when deterrence is appropriate, it might not work -- for example, against an enemy who is suicidal or invulnerable to a counterattack. Thus, it is more useful against governments, which have a return address and want to