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Back in 1976, all it took to bring the Korean Peninsula back to the brink of a war was a brawl over an attempt to trim a poplar tree. That escalated quickly into the death of two American GIs by ax-wielding North Korean soldiers. Three days later, with an aircraft carrier battle group and nuclear-capable B-52 bombers at the ready, the tree was chopped down.

For sure, the Demilitarized Zone that divides the Koreas is one of most volatile strips of Cold War-style weirdness left on the planet. And on Friday it was weirder than usual — with President Donald Trump's new top diplomat, Rex Tillerson, standing on one side of the North-South demarcation line with his coterie and North Korean soldiers standing just a meter (a few feet) away.

Fittingly enough, Tillerson arrived by helicopter at Camp Bonifas, a U.S. base on the edge of the DMZ named after one of the ax murder victims, Capt. Arthur Bonifas.

There were no axes this time. The North Korean soldiers on the other side of the line wielded cameras.

Tillerson made no public comments and quickly flew off to Seoul, but his DMZ detour comes a just day after he called years of U.S. policy toward North Korea a failure and vowed a comprehensive policy review under Trump.

"Diplomatic and other efforts of the past 20 years to bring North Korea to a point of denuclearization have failed," he told reporters on Thursday in Tokyo, reflecting a widely held but rarely publicly spoken view of many experts both in and outside of the U.S. government. "It is clear that a different approach is required."

Bleak though that 20 years of failure assessment may ring, Tillerson might just as well have tacked on a few decades more.

Well before going nuclear, North Korea has dogged every U.S. president since Harry Truman.

The 1950-53 Korean War, fought under Truman, is technically still going, since it ended with a truce that has yet to be negotiated into an actual peace treaty. It was Gerald Ford who ordered "Operation Paul Bunyan," the massive show of force that followed the ax murder incident in 1976. Bill Clinton considered pre-emptive strikes in 1994, then tried increased engagement, which failed and was buried for good in 2002, when George Bush included North Korea on his "axis of evil" in a State of the Union speech.

What path Trump will ultimately choose is a mystery.

On the campaign trail he said he was open to the idea of meeting directly with North Korean leader Kim Jong Un — flippantly adding that they might best talk over hamburgers. But he has also hinted at a hawkish approach or shifting the onus almost completely on to Beijing, which is North Korea's biggest trading partner and economic lifeline.

In Tokyo, which hosts tens of thousands of U.S. troops and is within North Korean missile range, Tillerson stressed that the policy review is underway. It would presumably analyze and weigh the benefits and risks of the full gamut of foreign policy tools at Washington's disposal. That could range from pre-emptive attacks on its nuclear facilities and precision strikes aimed at killing its leaders to negotiation-based diplomatic engagement.

For the moment, relations are following the trajectory set by Barack Obama, which focused on exerting pressure on the North through strengthening regional alliances, tougher economic sanctions in response to nuclear tests or missile launches and a flat refusal to talk without Pyongyang first taking concrete moves toward denuclearization.

But attention-demanding problems are increasing:

— The U.S. and South Korea are currently holding their biggest-ever annual joint military exercises, which are seen by the North as a dress rehearsal for invasion. Washington and Seoul claim the maneuvers are purely defensive, but they bring a rise in tensions that increases the possibility of a clash, either intentional or in response to an accident or misjudgment in the field.

— North Korea just last week fired four ballistic missiles into the Japan Sea, reportedly coming to within just 200 kilometers (120 miles) of Japan's shoreline.

— The U.S. and South Korea are planning to set up the state-of-the-art missile defense system known as THAAD, which along with the predictable opposition from Pyongyang has antagonized Beijing because it can monitor activity in China as well.

— North Korea says it is in the final stages of developing an intercontinental ballistic missile that could reach the U.S. mainland, and fit it with a nuclear warhead. More tests of both nuclear devices and long-range missiles are almost a certainly on the near future, though no one can predict when.

For Tillerson and Trump — and for America's nervous Asian allies looking to them for leadership — acknowledging past failures will without doubt be a lot easier than finding future successes.

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Eric Talmadge has been the AP's Pyongyang bureau chief since 2013.