When U.S. President Donald Trump strolled onto a red-carpeted stage to greet North Korea’s Kim Jong Un for the photo-op to end all photo-ops, the cameras flashed furiously and millions of viewers around the world took careful note of every expression and every gesture that was exchanged between the two leaders.

It was the first time a sitting U.S. president had met face-to-face with the ruler of one of the world’s most isolated and brutal regimes and the stakes were high.

Just days before the pair met at a luxury resort on Singapore’s Sentosa Island on Tuesday, Trump told reporters he would know “pretty quickly” whether his counterpart was serious about their discussion on nuclear disarmament. It’s part of the reason why anxious spectators in the U.S., South Korea, and all over watched for any telltale signs in the two leaders’ body language for an indication of how the relationship and the talks would fare in the hours and days to come.

From the initial handshake to the choice of footwear, a communications expert decodes the optics behind Trump and Kim’s historic summit.

Handshake history

Unlike Trump’s famous handshakes with French President Emmanuel Macron – one of them lasted nearly 30 seconds and a recent one left the American president with a white imprint on his hand from the pressure of Macron’s grip – or his awkwardly long clasp with Japanese Prime Minister Shinzo Abe in February, the one with Kim was relatively tame by comparison.

The 13-second-long first handshake between Trump and Kim appeared to be civil as the two stood on the stage and grinned for the cameras. Laura Babcock, the president of PowerGroup Communications, noted that Trump didn’t try to aggressively pull Kim in towards him, as he has done with other world leaders, during the handshake.

“In this particular case, they held the handshake right in the middle,” she told CTV News Channel on Tuesday.

However, Trump did briefly place his left hand upon Kim’s upper right arm during the encounter, which Babcock attributed to a display of strength.

“[It’s] a way of asserting dominance,” she explained. “Later you saw Kim try to do that to him, they would touch each other’s backs and arms. It’s a way of saying, ‘I’m the one in charge of this particular summit.’”

Heightened awareness

Kim appeared at the summit clad in his usual Mao-style buttoned up suit, his horn-rimmed glasses, and a pair of shoes that raised some eyebrows and his apparent stature.

As he stepped foot on the stage, viewers were quick to point out the sizeable heel on the black shoes the North Korean leader sported during the visit. It’s unclear exactly how much of a boost the heels gave him, but at approximately 5’7” tall, Kim is nearly eight inches shorter than the 6’3” tall Trump.

Babcock said Kim’s choice of footwear was most likely intentional to offset some of the disparity in height.

“It’s very important,” she said. “People do ascribe certain power to height. In a case like this, where there is such a height differential, that would be strategic.”

“A lot of photos wouldn’t go all the way down to the shoes of course and so it would look a little bit more powerful.”

The communications expert noted that wearing lifts or heeled shoes or sitting in a higher chair is a common technique for anyone wishing to appear taller than their counterpart.

As examples, Babcock said television hosts will often raise their seats higher than their guests during live interviews and former American presidents have been known to make their couch cushions softer so that visiting dignitaries will sink into them during meetings.

“[It] is very important because a lot of people don’t really get down to the details. They don’t necessarily listen for too long or get past the headlines, but they do look at the images and that’s why they say a picture tells a thousand words,” she said.

Backdrop politics

Along with their mannerisms and style, the two leaders made a statement with the impressive backdrop they stood in front of during the photo-op.

Trump and Kim walked on a red carpet through the open-air hallways to meet each other before a display of six American flags interlocked with six North Korean ones. Although the symbolic background was intended to denote peaceful cooperation between the two nations, many Americans took offense to their flag hanging side-by-side with the flag of a country known for its human rights abuses.

The presentation of the flags and the photo-op itself have been criticized in numerous outlets for “normalizing” Kim Jong Un and legitimizing his harsh regime.

“This is why presidents haven’t wanted to do this photo-op, any of them could have,” Babcock said. “This in fact, legitimizes the dynasty in North Korea and so other presidents have said, ‘No way am I going to give that up. Maybe, at the end of a real denuclearization I might give you that, but not upfront.’”

Babcock said many people view Trump’s decision to formally meet with Kim before a concrete agreement on nuclear weapons was agreed upon as a strategic error. She said the flags lined up like that just added insult to the injury perceived by those who were against the summit.

“It denigrates the flag to many who saw that image,” she said. “It sends a much stronger message than I think Trump was even aware of.”