Trump's tariff threats, a cold case is cracked & the Met Gala: The Morning Rundown

Good morning, NBC News readers.

The first Monday in May has become synonymous with a fashion fiesta on the steps of New York's Metropolitan Museum of Art.

But before you get to the fun of deciding who summed up this year's "camp" theme best, here's what we're watching today.

China is playing a long game against the U.S., experts say

President Donald Trump sent stock prices on a roller coaster ride Monday after his sudden announcement that he intended to impose tariffs on almost all goods imported from China by Friday.

One group that was not surprised? The Chinese, several experts say.

The Chinese strategy, one expert said, is basically to let Trump bluster and then resume talking with more serious administration officials.

Many economists also disagree with Trump's claims that tariffs already in place are boosting the American economy.

"His assertion generally that the Chinese are paying these tariffs is just simply nonsense. It’s a complete misunderstanding of how tariffs work," one senior economist said.

Mnuchin tells Congress: No dice on Trump taxes

Treasury Secretary Steven Mnuchin rejected House Democrats’ request for Trump’s tax returns on Monday, failing for the third time to meet a congressional deadline to turn over the documents.

The move raised the stakes in the fight between the administration and Congress over the documents, making a legal battle to obtain them all but certain.

'A prudent repositioning of assets'

The decision to move the USS Abraham Lincoln Carrier Strike Group and Air Force bombers to the Middle East was based on Iranian threats to U.S. military forces and civilians at multiple locations, according to U.S. officials and a defense official.

The officials warned that Iran has proxy forces operating in Iraq, Syria, Yemen and other parts of the region that could rise up and target Americans. "We are taking this threat reporting very seriously," one U.S. official said.

Others are more skeptical of the move.

"The Trump administration is laying the groundwork for an unnecessary new war of choice which Congress has not authorized and which the American people do not want," said Dylan Williams, vice president of the J Street advocacy group, which has sharply criticized the administration’s approach to Iran.

As Europe closes its borders, Wales becomes a 'nation of sanctuary'

“There is a phrase, ‘Welcome to the valleys and the hillsides of Wales,’ because that is how we’ve always been — a nation that welcomes people,” said Jane Hutt, a veteran lawmaker who is responsible for implementing a refugee resettlement program in the small country.

While countries throughout Europe have closed their borders to asylum-seekers and looked to discourage those who arrive from settling permanently, Wales says it is intent on opening its doors to those fleeing war and persecution.

“Refugees and asylum-seekers are and will become doctors, carpenters, farmers, radiographers making a contribution to the community," added Hutt, outlining her vision for the plan.