As Michael has recently reminded us, the possession of nuclear weapons by two adversaries may lessen the chances of all-out war, but it does not prevent — and may even encourage — more limited forms of conflict. Western strategists have held this view since at least the 1950s, and lately have used it to explain the pattern of Indo-Pakistani clashes since the nuclear tests of 1998. (See The Stability-Instability Paradox, Nov. 2, 2010.)

The same phenomenon now appears to be at work on the Korean Peninsula.

In Korea as elsewhere, it’s not necessarily the more powerful actor that reaps the benefit of mutual nuclear deterrence. What Thomas Schelling defined as a competition in risk-taking mainly works in favor of those less averse to risk. That doesn’t mean that North Korea has been completely reckless; it simply means that Seoul and Washington have been more cautious. Before the shelling of Yeonpyeong Island last week, and even before the sinking of the ROK ship Cheonan off Baeknyeong Island in March, KPA artillery units had started to fire occasional barrages in the direction of the islands, testing South Korean tolerance by small steps. As the Chosun Ilbo observes, the shelling fell on the northern side of the Northern Limit Line (NLL) in January, then south of the NLL in August. Neither incident garnered more than a verbal response. Now that the South Koreans have fired back — and say they will alter the rules of engagement in response to this incident — the North may well conclude it has started to discover the limits of Seoul’s tolerance.

The Role of Nuclear Weapons

Some maintain that by holding Seoul hostage to artillery fire, North Korea has long had the political or functional equivalent of the Bomb. That might explain some of its aggressiveness in the military incidents and bombings of the 1960s through the 1980s. But in hindsight, perhaps this factor has never really loomed so large in Pyongyang’s own thinking. As Victor Cha pointed out at an Aug. 31, 2010 talk at CSIS, the long gap between the Cheonan and the massacres of yore suggests that something important has changed lately, and that something seems to have been the second, more successful nuclear test.

We might also ask what changed in the late 1980s. Why, a full decade before the onset of the Sunshine Policy (ca. 1998), did North Korea stop trying to assassinate South Korean leaders, blow up airliners, or attack American military ships or planes? And why was it necessary to test a couple of nuclear devices before reverting to the bad habits of yesteryear? The answers aren’t clear, but a couple of points stand out.

First, without a nuclear-armed superpower ally behind them, North Korean leaders may have hesitated to act too provocatively, even with the advantage of having Seoul under the gun. Second, in the Sunshine period, they had little incentive to behave that way. Only after North-South relations had entered their downturn (ca. 2008), and only after North Korea had the Bomb (ca. 2009) would this sort of behavior seemed at all attractive.  We needn’t even invoke the succession or other special factors to explain it — this is the historic norm for North Korean conduct toward the South.

The D-word

So why did North Korea start performing nuclear tests during the era of good feelings (comparatively speaking)? One answer is, possessing a demonstrated nuclear capability was seen to protect against regime change. The shift in Kim Jong Il’s thinking can be seen rather plainly in a Ministry of Foreign Affairs (MFA) statement that appeared in KCNA on April 6, 2003, when North Korea suddenly embraced the doctrine of deterrence wholesale:

Only the physical deterrent force, tremendous military deterrent force powerful enough to decisively beat back an attack supported by any ultra-modern weapons, can avert a war and protect the security of the country and the nation. This is a lesson drawn from the Iraqi war.

The U.S is seriously mistaken if it thinks that the DPRK will accept the demand for disarming while watching one of the three countries the U.S. listed as part of an “axis of evil” already subject to the barbarous military attack.

Before then, deterrence was just a Yankee imperialist shibboleth that KCNA mentioned only to sneer at.

April 6, 2003 is also just about when it became plain that the 3rd Infantry Division of the U.S. Army was meeting no serious resistance on the doorstep of Baghdad. North Korean leaders have always paid close attention to distant military events, as Joe Bermudez convincingly shows in the latest issue of KPA Journal. And — as noted in the MFA statement itself — it scarcely could have escaped Kim Jong Il’s attention that he was a charter member of the Axis of Evil. Thus, when North Korea announced its first nuclear test in October 2006, it called the event “the new measure to be taken to bolster the war deterrent for self-defence.”

But as an amulet against regime change, a nuclear deterrent cuts both ways; it protects a regime whether it’s defensively minded or inclined to aggression — at least on a limited scale.

Most Western experts don’t assume that the North Korean military actually has nuclear warheads small enough to place on its missiles. But the shelling of Baeknyeong suggests either that it does, or that Pyongyang is engaged in one great bluff.