17 April 2013. The dangers involved are now on clear display in the escalating crisis in North Korea as the United States seeks to strike a delicate balance between deterring an unknown adversary and reassuring a nervous ally. What's more, the drama plays out in full view of an international audience, some of whom are watching for clues about the utility of nuclear weapons in the 21st Century.

When Kim Jong Un began his sabre rattling last February Washington feared that a weak response would only tempt the boy king down the dangerous course of nuclear brinksmanship and further unsettle its partner in the South. In a textbook display of allied solidarity, US and South Korean troops conducted a massive joint military exercise to signal their capability and demonstrate America's enduring commitment to South Korea's security. In March tensions escalated. Responding to new threats of nuclear strikes Washington sent two nuclear-capable B-2 bombers on a training mission in South Korea.

Strategic Relations
The problem is that such moves often provoke the very conflict they seek to deter. Although weakness tempts aggression, so too does fear. Credible threats might induce restraint in an opportunist or adventurer, but they are more likely to provoke the weak or wounded to lash out. Hence, the biggest challenge for Washington and its regional allies is accurately assessing the motivations behind Pyongyang's provocations, a difficult task given that the opaqueness of the North Korean regime. But to the degree to which North Korea's nuclear programme is driven by a desire to deter an American attack; U.S. threats are likely to increase the sense of danger and thus the determination to acquire an operational nuclear capability.

Of course most Americans would find it odd that Pyongyang fears an unprovoked attack. But that is precisely the point. Given the nature of the North Korean regime and its international isolation, the likelihood is quite high that it interprets American behaviour in ways that we would find puzzling if not completely bizarre.

Memories of the Cold War
If deterring the North is fraught with dangers, the situation is not much better when it comes to reassuring the South. During the Cold War, Washington was afraid that widespread fears of abandonment could demoralise allied populations in Europe and Asia, weakening their willingness to resist communist extortion. Although the nightmare of monolithic communism is long gone, Washington retains an interest in projecting the image of a reliable ally in Asia--not only to deter a North Korean attack on the South, but also to contain the political influence of a rising China.

But in reassuring Seoul, Washington might embolden its ally to undertake riskier policies than it otherwise might. In international relations as in private affairs, a blank check can turn a saver into a spendthrift. Given the strength of the American commitment it is not surprising, though no less unsettling, that South Korean President Park Geun-hye this month authorised her military to deliver a strong and immediate response to any North Korean provocation "without any political consideration". While this is a textbook effort to increase the credibility of deterrence, it risks drawing the United States into a war based on the judgments made by a South Korean field commander.

The Paradox of Conflict
The example points to a more general paradox: to succeed in deterring an adversary requires one to make threats that one may not wish to carry out if deterrence fails. The lesson was not lost on President John F. Kennedy. Upon learning that the Soviet Union had deployed nuclear weapons to Cuba he was reminded of his previous commitment to prevent such an eventuality and quipped, "Last month I should have said we don't care."

Luckily deterrence sometimes succeeds and the earlier judgment of an American diplomat may still hold: "The North Koreans do not respond to pressure. But without pressure they do not respond." Moreover, the standoff on the North Korean peninsula is surely being watched carefully by the Mullah's in Tehran. As with missiles in Cuba, indifference, alas, is not an option.

Bild: Photocase / Designbüro Marx