When U.S. President Donald Trump strolled onto a red-carpeted stage to greet North Korea鈥檚 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鈥檚 most isolated and brutal regimes and the stakes were high.

Just days before the pair met at a luxury resort on Singapore鈥檚 Sentosa Island on Tuesday, Trump told reporters he would know 鈥減retty quickly鈥� whether his counterpart was serious about their discussion on nuclear disarmament. It鈥檚 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鈥� 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鈥檚 historic summit.

Handshake history

Unlike Trump鈥檚 famous handshakes with French President Emmanuel Macron 鈥� 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鈥檚 grip 鈥� 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鈥檛 try to aggressively pull Kim in towards him, as he has done with other world leaders, during the handshake.

鈥淚n this particular case, they held the handshake right in the middle,鈥� she told CTV News Channel on Tuesday.

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

鈥淸It鈥檚] a way of asserting dominance,鈥� she explained. 鈥淟ater you saw Kim try to do that to him, they would touch each other鈥檚 backs and arms. It鈥檚 a way of saying, 鈥業鈥檓 the one in charge of this particular summit.鈥欌��

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鈥檚 unclear exactly how much of a boost the heels gave him, but at approximately 5鈥�7鈥� tall, Kim is nearly eight inches shorter than the 6鈥�3鈥� tall Trump.

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

鈥淚t鈥檚 very important,鈥� she said. 鈥淧eople do ascribe certain power to height. In a case like this, where there is such a height differential, that would be strategic.鈥�

鈥淎 lot of photos wouldn鈥檛 go all the way down to the shoes of course and so it would look a little bit more powerful.鈥�

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.

鈥淸It] is very important because a lot of people don鈥檛 really get down to the details. They don鈥檛 necessarily listen for too long or get past the headlines, but they do look at the images and that鈥檚 why they say a picture tells a thousand words,鈥� 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 鈥渘ormalizing鈥� Kim Jong Un and legitimizing his harsh regime.

鈥淭his is why presidents haven鈥檛 wanted to do this photo-op, any of them could have,鈥� Babcock said. 鈥淭his in fact, legitimizes the dynasty in North Korea and so other presidents have said, 鈥楴o way am I going to give that up. Maybe, at the end of a real denuclearization I might give you that, but not upfront.鈥欌��

Babcock said many people view Trump鈥檚 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.

鈥淚t denigrates the flag to many who saw that image,鈥� she said. 鈥淚t sends a much stronger message than I think Trump was even aware of.鈥�