When former US President Bill Clinton travelled to North Korea in 2009 on a humanitarian mission to free two American journalists, he delivered strict instructions to his team ahead of their meeting with dictator Kim Jong Il: "We're not smiling."
In several photos, including a formal portrait with their hosts in Pyongyang, Clinton and his aides kept their game faces on - looking serious and determined, befitting the tone of the mission, according to a person familiar with the trip.
President Donald Trump took a decidedly different approach at the weekend when he welcomed a North Korean official to the White House for the first such meeting in 18 years. Trump beamed as Kim Yong Chol - a former spy chief accused of masterminding the sinking of a South Korean Navy vessel in 2010 that killed 46 sailors - presented him with a cartoonishly oversize envelope containing a letter from Kim Jong Un, the nation's dictator. The two posed for photos in the Oval Office.
The warm display left some former US officials who've negotiated with North Korea arguing that Trump had already handed Pyongyang another public relations victory before winning concessions on its nuclear programme. "No question this is speed-dating," said Christopher Hill, a former State Department diplomat who led the US delegation in the Six-Party Talks with North Korea during the George W. Bush Administration. He recalled being rebuffed in his bid to deliver a letter from Bush to Kim Jong Il - in a standard-size envelope. By contrast, Hill said, the North Koreans already "have gotten the whole enchilada" from Trump.
The question of how to engage with a brutal, authoritarian regime has been a challenge for most presidents, but it has taken on heightened sensitivity as Trump prepares to meet Kim Jong Un in Singapore on June 12. No sitting president has ever met with a North Korean leader, and the summit will produce images that ricochet instantly around the globe.