(CNN) The iceberg wedge salads, dripping with blue cheese dressing, had just been served on the terrace of Mar-a-Lago Saturday when the call to President Donald Trump came in: North Korea had launched an intermediate-range ballistic missile , its first challenge to international rules since Trump was sworn in three weeks ago.

The launch, which wasn't expected, presented Trump with one of the first breaking national security incidents of his presidency. It also noisily disrupted what was meant to be an easygoing weekend of high-level male bonding with the more sobering aspects of global diplomacy.

Sitting alongside Japanese Prime Minister Shinzo Abe, with whom he'd spent most of the day golfing, Trump took the call on a mobile phone at his table, which was set squarely in the middle of the private club's dining area.

This was the first missile test by Pyongyang since US President Donald Trump took office.

This was the first missile test by Pyongyang since US President Donald Trump took office.

Kim celebrates with soldiers after the missile test, which North Korean state media claimed was successful.

Kim celebrates with soldiers after the missile test, which North Korean state media claimed was successful.

Kim was present at the site and personally gave the order for the launch, state media reported.

Kim was present at the site and personally gave the order for the launch, state media reported.

The Pukguksong-2 was launched on Sunday, according to North Korean state media.

The Pukguksong-2 was launched on Sunday, according to North Korean state media.

North Korean leader Kim Jong Un looks on as the country tests a new intermediate-range ballistic missile.

North Korean leader Kim Jong Un looks on as the country tests a new intermediate-range ballistic missile.

As Mar-a-Lago's wealthy members looked on from their tables, and with a keyboard player crooning in the background, Trump and Abe's evening meal quickly morphed into a strategy session, the decision-making on full view to fellow diners, who described it in detail to CNN.

News of Pyongyang's launch had emerged an hour earlier, as Trump was preparing for dinner in his residence. Officials had concluded the Musudan-level missile flew 310 miles off North Korea's eastern coast before crashing into the Sea of Japan.

For the new commander in chief, the launch was his first brush with the hermit regime's saber-rattling, which along with heated rhetoric from the young leader Kim Jong-un has spooked the country's neighbors. During his pre-election intelligence briefings, Trump requested supplemental information about North Korea from US intelligence officials. National security analysts have identified the nation's nuclear program as one of the imminent threats facing Trump as he begins his tenure in the White House.

In his talks with Abe at the White House on Friday, the North Korea threat weighed heavily. Abe said during a concluding news conference that he and Trump had agreed to "strongly demand" the country "abandon (its) nuclear and ballistic missile program." They departed a short time later for Florida.

On Saturday evening, as the two men walked through Mar-a-Lago's ornate wrought-iron doors on their way to dinner, neither responded to questions about the launch from reporters.

Swanning through the club's living room and main dining area alongside Abe, Trump was -- as is now typical -- swarmed with paying members, who now view dinner at the club as an opportunity for a few seconds of face time with the new President.

But as he sat down for the planned working dinner with Abe, whose country is well within range of North Korea's missiles, it was clear his counterpart felt it necessary to respond to the test. The launch occurred just before 8 a.m. on Sunday morning in Japan.

Trump's national security adviser Michael Flynn and chief strategist Steve Bannon left their seats to huddle closer to Trump as documents were produced and phone calls were placed to officials in Washington and Tokyo.

Presidents always travel with secure communications equipment, even when they're on vacation. A Sensitive Compartmented Information Facility, known as a SCIFF, also comes along. The tent-like structure can fit inside a hotel room and allows a president to conduct sensitive phone calls without the risk of being detected by recording devices.

At Mar-a-Lago on Saturday, it had not been immediately clear whether Trump utilized that equipment, but White House spokesman Sean Spicer told reporters Monday he had.

"The President was briefed in a SCIFF prior to dinner," Spicer told reporters Monday. "They were reviewing the logistics for the press conference ... President was subsequently briefed in a classified setting."

On Saturday night, the patio was lit only with candles and moonlight, so aides used the camera lights on their phones to help the stone-faced Trump and Abe read through the documents.

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Even as a flurry of advisers and translators descended upon the table carrying papers and phones for their bosses to consult, dinner itself proceeded apace. Waiters cleared the wedge salads and brought along the main course as Trump and Abe continued consulting with aides.

First lady Melania Trump and Abe's wife, Akie, remained seated across from their husbands, speaking quietly through a translator amid the activity. Earlier in the day, the women had toured a nearby Japanese garden and visited the gothic Bethesda-by-the-Sea church, where Trump and his wife were married in 2005.

Eventually Trump and Abe, along with their collection of aides, stood and moved from the dining terrace and toward a marble-trimmed ballroom, whose gilded columns were concealed by more sober-looking black drapes.

Standing in front of an American and Japanese flag, a stern-faced Abe called the launch "absolutely intolerable," and insisted North Korea adhere to United Nations Security Council resolutions barring it from testing of ballistic missiles.

Trump, in his short remarks, didn't mention the launch. He used a short statement to vow support for Japan instead.

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"I just want everybody to understand and fully know that the United States of America stands behind Japan, its great ally, 100%," Trump said.

He declined to read from a set of prepared remarks, which photographers captured images of, that were resting on his podium. Those remarks did mention the missile test specifically and vowed cooperation between allies to "safeguard and protect" against North Korea's "provocative acts."

"That was a joint statement we decided not to make," a senior administration official said afterward, explaining why those remarks were cast aside. Because Abe spoke first, and then Trump, there was "no need for communique," the official said.

Trump left the impromptu briefing room without taking questions, having delivered the first emergency foreign policy statement of his presidency,

But even as he confronted one of the gravest matters of his office, Trump nonetheless found it impossible to resist dropping in on a nearby wedding reception, already underway in his treasured Grand Ballroom. Trump designed and built the space himself after purchasing Mar-a-Lago in the 1980s.

Entering the ornate room, Trump took a photo with the bride and her bridesmaids, who posed in red gowns next to the commander in chief, mimicking his signature thumbs-up.

Then he grabbed a microphone.

"I saw them out on the lawn today," Trump said of the bride and groom, who were standing nearby. "I said to the Prime Minister of Japan, I said, 'C'mon Shinzo, let's go over and say hello.' "

"They've been members of this club for a long time," Trump said of the newlyweds. "They've paid me a fortune."