King Charles III’s four-day swing in the United States kicks off in earnest today as the monarch meets first with President Donald Trump and then delivers an address to a joint session of Congress before attending a state dinner back at the White House.

It’s a jam-packed day where every utterance will be scrutinized on both sides of the Atlantic, as viewers look to dissect exactly what the king means by analyzing what he says and, more importantly, what he doesn’t say.

Here’s what to watch.

1) Trump and Charles optics

Trump and the king will meet this morning in the Oval Office, where the president has hosted dozens of foreign leaders in the past 15 months from Ukrainian President Volodymyr Zelenskyy to Saudi Crown Prince Mohammed bin Salman.

The meeting is, for now, closed press, meaning no members of the media will be in the room to ask the president and king questions or observe their interactions.

Trump, however, has been known to change the rules of engagement at the last minute so there’s always a chance. That could set up a wild scene.

British monarchs typically engage with the press in controlled environments, while Trump is known for his freewheeling style and is just as likely to put his guest in the hot seat as the press. Last month, for example, he made a joke about Pearl Harbor during an Oval event with Japanese Prime Minister Sanae Takaichi. He also made a joke about the Nazis in front of German Chancellor Friedrich Merz.

Maybe he knows a good one about the War of 1812.

2) Parallels with the Queen’s address to Congress

Queen Elizabeth II was the first monarch to address a joint session of Congress and in her 1991 speech, she memorably spoke about the importance of keeping NATO together.

Will Charles follow suit? Reports suggest yes but how forcefully remains an open question. Trump’s feelings on NATO are not a secret. He’s called it a “paper tiger” and disparaged the nations that make up the alliance.

Standing up for NATO will be seen as a rebuke of the president, his host. Saying nothing about NATO will be seen as a missed opportunity to remind Congress and the American people of its importance to the world.

The late queen, speaking amid the collapse of the Soviet Union, called on the U.S. to never forget why NATO should stand together.

“The swift and dramatic changes in eastern Europe in the last decade have opened up great opportunities for the people of those countries, they are finding their own paths to freedom,” the queen said. “But the paths would have been blocked if the Atlantic Alliance had not stood together, if your country and mine had not stood together. Let us never forget that lesson.”

3) Wednesday offers another chance to stress the alliance

The king and queen will travel to New York on Wednesday and stop at the 9/11 memorial in lower Manhattan to attend a wreath laying. New York Mayor Zohran Mamdani and former Mayor Michael Bloomberg are expected to attend.

Sixty-seven people from the United Kingdom were killed in the Sept. 11 terrorist attacks and British forces were deployed to Afghanistan in the aftermath. It was the only time NATO invoked Article V, the compact that says an attack on one country in the alliance is an attack on all.

The king will also visit Arlington National Cemetery in Virginia, where there are 32 British servicemembers from multiple wars. Both are symbols of Britain’s commitment to the defense ties.

Those visits come after NATO allies, including U.K. Prime Minister Keir Starmer, criticized Trump this year for suggesting that allied forces stayed “a little off the front lines” in the war in Afghanistan. Starmer called the remarks “insulting and frankly appalling.”