(Bloomberg View) -- Think of the North Korean problem as a set of two dangerous streams of activity, moving rapidly toward each other. One is the increasing range of the Kim Jong Un regime's intercontinental ballistic missiles, which are now verifiably in the 3,000 to 4,000 mile range -- probably far enough to strike the continental U.S.
The other stream consists of the North Koreans' efforts to produce reliable nuclear weapons small enough to affix to the warheads of those ballistic missiles. Both U.S. intelligence services and common sense tell us that they are moving rapidly to accomplish this -- the technology is well known, and U.S.-led international sanctions are having little effect.
The bad news is that they will cross, possibly in as little as 18 to 24 months. The regime will then present a clear and present danger to the U.S., especially when matched with the incendiary rhetoric of the dictator Kim Jong Un. This will present President Donald Trump with his most difficult decision, as he was warned about before taking office by his predecessor, Barack Obama.
The first thing to acknowledge is that over the past two decades, most diplomatic approaches -- negotiations, sanctions and trying to persuade China, which keeps North Korea afloat economically, to rein in the Kim dynasty -- have been tried without significant results. So it’s little wonder that the Trump administration has put military options on the table.
There are clear precedents in international law that would tempt a president to undertake a military first strike under the doctrine of pre-emptive attack. (Israel's 2007 "Operation Orchard" airstrike on a suspected Syrian nuclear site comes to mind.) But a president also has to consider the downsides of using force. These could include setting off chaos on the peninsula through attempts at regime change, or devastating second-order effects -- war that kills hundreds of thousands, including tens of thousands of Americans.
The good news is that, eventually, the U.S. and South Korea would prevail in a widespread military conflict. But the cost would be extremely high, given that virtually any assault would probably cause Kim to believe that the strategy included killing him and replacing him with a more pliable substitute. Undoubtedly, he would unleash his conventional artillery and other capabilities against the world's largest human shield: the 25 million people in the greater Seoul area. And the temptation for him to use his nuclear arsenal at that point would be high, against South Korea and possibly Japan.
Even if the U.S. attempted a pre-emptive strike with a strategically telegraphed goal of convincing Kim it was were “only” taking out his nuclear capability -- a very delicate message to say the least -- it wouldn't be easy. The U.S. military don’t have a good fix on the precise location of all elements of his nuclear program, North Korea provides very difficult physical targets (mountains, deeply buried-command-and control facilities), and the regime has invested in keeping a great deal of their weaponry mobile to evade detection.
Any broader pre-emption would likely begin with a widespread strike against Pyongyang’s offensive weapons systems (notably artillery batteries arrayed against Seoul, surface-to-surface missiles, and military aircraft). Using cyberattacks to “blind” the North Koreans' communications networks, undermine their targeting and their access to the GPS, and above all to neutralize their nuclear capability, would be difficult.
All this would require perhaps three or four Navy carrier strike groups -- there are only four deployed around the globe right now -- significant long-range air support, coordinated missile strikes from South Korean territory, broader deployment of defensive missile technology such as the Thaad system that is (controversially) being deployed in the south now, and a high-end special forces campaign -- all of which would be very difficult to execute with tactical surprise. Pyongyang would almost undoubtedly see it coming, and have time to wreak enormous damage.
Soon enough, this would almost certainly lead to engagement on a level of World War II or the Korean War, with hundreds of thousands of casualties. Bad choice.
So what are we left with? We still have a shrinking window of time in which to try (again) the diplomatic and economic approaches. The only way things would end differently is if we could get China to finally agree to exert real leverage on Kim's regime. The Chinese would want to extract a price for doing so -- which could include a combination of more of a free hand in the South China Sea, reduced U.S. engagement with South Korea, fewer military exercises in the region, weakening U.S. security guarantees to Taiwan, favorable trade relations, no secondary sanctions on Chinese businesses, and guarantees that the Korean peninsula would remain divided.
Any of this might be too high a price for the Trump administration. Yet even the president's secretary of defense, Jim Mattis, says that in comparison, a war would be “catastrophic.” This from a man who has personally overseen some of the worst fighting in the Middle East over the past decade.
The best outcome to the current crisis, then, may be simply living with North Korean nuclear weapons and relying on Kim understanding that using one of his weapons would be signing his own death warrant, to say nothing of the carnage of his loyal subjects. This would be betting that, much as was the case in the Cold War, mutual assured destruction can keep the peace.
Perhaps it doesn’t have the satisfaction of cutting a clever deal with China or the shock and awe of a military strike; but at the moment it looks increasingly like the least-worst option on the table.
This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.
James Stavridis, a retired U.S. Navy admiral and former military commander of NATO, is dean of the Fletcher School of Law and Diplomacy at Tufts University. His most recent book is "Sea Power: The History and Geopolitics of the World's Oceans."
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