When he approved a campaign to reopen shipping in the Red Sea by bombing the Houthi militant group into submission, President Trump wanted to see results within 30 days of the initial strikes two months ago.

By Day 31, Mr. Trump, ever leery of drawn-out military entanglements in the Middle East, demanded a progress report, according to administration officials.

But the results were not there. The United States had not even established air superiority over the Houthis. Instead, what was emerging after 30 days of a stepped-up campaign against the Yemeni group was another expensive but inconclusive American military engagement in the region.

The Houthis shot down several American MQ-9 Reaper drones and continued to fire at naval ships in the Red Sea, including an American aircraft carrier. And the U.S. strikes burned through weapons and munitions at a rate of about $1 billion in the first month alone.

It did not help that two $67 million F/A-18 Super Hornets from America’s flagship aircraft carrier tasked with conducting strikes against the Houthis accidentally tumbled off the carrier into the sea.

By then, Mr. Trump had had enough.

Steve Witkoff, his Middle East envoy, who was already in Omani-mediated nuclear talks with Iran, reported that Omani officials had suggested what could be a perfect offramp for Mr. Trump on the separate issue of the Houthis, according to American and Arab officials. The United States would halt the bombing campaign and the militia would no longer target American ships in the Red Sea, but without any agreement to stop disrupting shipping that the group deemed helpful to Israel.

U.S. Central Command officials received a sudden order from the White House on May 5 to “pause” offensive operations.

Announcing the cessation of hostilities, the president sounded almost admiring about the militant Islamist group, despite vowing earlier that it would be “completely annihilated.”

“We hit them very hard and they had a great ability to withstand punishment,” Mr. Trump said. “You could say there was a lot of bravery there.” He added that “they gave us their word that they wouldn’t be shooting at ships anymore, and we honor that.”

Whether that proves to be true remains to be seen. The Houthis fired a ballistic missile at Israel on Friday, triggering air raid sirens that drove people off beaches in Tel Aviv. The missile was intercepted by Israeli air defenses.

The sudden declaration of victory over the Houthis demonstrates how some members of the president’s national security team underestimated a group known for its resilience. Gen. Michael E. Kurilla, the head of Central Command, had pressed for a forceful campaign, which the defense secretary and the national security adviser initially supported, according to several officials with knowledge of the discussions. But the Houthis reinforced many of their bunkers and weapons depots throughout the intense bombing.

Significantly, the men also misjudged their boss’s tolerance for military conflict in the region, which he is visiting this week, with stops in Saudi Arabia, Qatar and the United Arab Emirates. Mr. Trump has never bought into long-running military entanglements in the Middle East, and spent his first term trying to bring troops home from Syria, Afghanistan and Iraq.

What’s more, Mr. Trump’s new chairman of the Joint Chiefs of Staff, Gen. Dan Caine, was concerned that an extended campaign against the Houthis would drain military resources away from the Asia-Pacific region. His predecessor, Gen. Charles Q. Brown Jr., shared that view before he was fired in February.

By May 5, Mr. Trump was ready to move on, according to interviews with more than a dozen current and former officials with knowledge of the discussions in the president’s national security circle. They spoke on the condition of anonymity to describe the internal discussions.

“We honor their commitment and their word,” Mr. Trump said in remarks at the White House on Wednesday.

A White House spokeswoman, Anna Kelly, said in a statement to The New York Times that “President Trump successfully delivered a cease-fire, which is another good deal for America and our security.” She added that the U.S. military had carried out more than 1,100 strikes, killing hundreds of Houthi fighters and destroying their weapons and equipment.

The chief Pentagon spokesman, Sean Parnell, said the operation was always meant to be limited. “Every aspect of the campaign was coordinated at the highest levels of civilian and military leadership,” he said in an emailed statement.

A former senior official familiar with the conversations about Yemen defended Michael Waltz, Mr. Trump’s former national security adviser, saying he took a coordinating role and was not pushing for any policy beyond wanting to see the president’s goal fulfilled.

General Kurilla had been gunning for the Houthis since November 2023, when the group began attacking ships passing through the Red Sea as a way to target Israel for its invasion of Gaza.

But President Joseph R. Biden Jr. thought that engaging the Houthis in a forceful campaign would elevate their status on the global stage. Instead, he authorized more limited strikes against the group. But that failed to stop the Houthis.

Now General Kurilla had a new commander in chief.

He proposed an eight- to 10-month campaign in which Air Force and Navy warplanes would take out Houthi air defense systems. Then, he said, U.S. forces would mount targeted assassinations modeled on Israel’s recent operation against Hezbollah, three U.S. officials said.

Saudi officials backed General Kurilla’s plan and provided a target list of 12 Houthi senior leaders whose deaths, they said, would cripple the movement. But the United Arab Emirates, another powerful U.S. ally in the region, was not so sure. The Houthis had weathered years of bombings by the Saudis and the Emiratis.

By early March, Mr. Trump had signed off on part of General Kurilla’s plan — airstrikes against Houthi air defense systems and strikes against the group’s leaders. Defense Secretary Pete Hegseth named the campaign Operation Rough Rider.

At some point, General Kurilla’s eight- to 10-month campaign was given just 30 days to show results.

In those first 30 days, the Houthis shot down seven American MQ-9 drones (around $30 million each), hampering Central Command’s ability to track and strike the militant group. Several American F-16s and an F-35 fighter jet were nearly struck by Houthi air defenses, making real the possibility of American casualties, multiple U.S. officials said.

That possibility became reality when two pilots and a flight deck crew member were injured in the two episodes involving the F/A-18 Super Hornets, which fell into the Red Sea from the aircraft carrier Harry S. Truman within 10 days of each other.

Meanwhile, several members of Mr. Trump’s national security team were battling disclosures that Mr. Hegseth had endangered the lives of U.S. pilots by putting operational plans about the strikes in a chat on the Signal app. Mr. Waltz had started the chat and inadvertently included a journalist.

American strikes had hit more than 1,000 targets, including multiple command and control facilities, air defense systems, advanced weapons manufacturing facilities and advanced weapons storage locations, the Pentagon reported. In addition, more than a dozen senior Houthi leaders had been killed, the military said.

But the cost of the operation was staggering. The Pentagon had deployed two aircraft carriers, additional B-2 bombers and fighter jets, as well as Patriot and THAAD air defenses, to the Middle East, officials acknowledged privately. By the end of the first 30 days of the campaign, the cost had exceeded $1 billion, the officials said.

So many precision munitions were being used, especially advanced long-range ones, that some Pentagon contingency planners were growing increasingly concerned about overall stocks and the implications for any situation in which the United States might have to ward off an attempted invasion of Taiwan by China.

And through it all, the Houthis were still shooting at vessels and drones, fortifying their bunkers and moving weapons stockpiles underground.

The White House began pressing Central Command for metrics of success in the campaign. The command responded by providing data showing the number of munitions dropped. The intelligence community said that there was “some degradation” of Houthi capability, but argued that the group could easily reconstitute, officials said.

Senior national security officials considered two pathways. They could ramp up operations for up to another month and then conduct “freedom of navigation” exercises in the Red Sea using two carrier groups, the Carl Vinson and the Truman. If the Houthis did not fire on the ships, the Trump administration would declare victory.

Or, officials said, the campaign could be extended to give Yemeni government forces time to restart a drive to push the Houthis out of the capital and key ports.

In late April, Mr. Hegseth organized a video call with Saudi and Emirati officials and senior officials from the State Department and the White House in an effort to come up with a sustainable way forward and an achievable state for the campaign that they could present to the president.

The group was not able to reach a consensus, U.S. officials said.

Now joining the discussions on the Houthi operation was General Caine, Mr. Trump’s new Joint Chiefs chairman, who was skeptical of an extended campaign. General Caine, aides said, was concerned about supply of assets he thought were needed for the Pacific region.

Also skeptical of a longer campaign were Vice President JD Vance; the director of national intelligence, Tulsi Gabbard; Secretary of State Marco Rubio; and Mr. Trump’s chief of staff, Susie Wiles. Mr. Hegseth, people with knowledge of the discussions said, went back and forth, arguing both sides.

But Mr. Trump had become the most important skeptic.

On April 28, the Truman was forced to make a hard turn at sea to avoid incoming Houthi fire, several U.S. officials said. The move contributed to the loss of one of the Super Hornets, which was being towed at the time and fell overboard. That same day, dozens of people were killed in a U.S. attack that hit a migrant facility controlled by the Houthis, according to the group and aid officials.

Then on May 4, a Houthi ballistic missile evaded Israel’s aerial defenses and struck near Ben-Gurion International Airport outside Tel Aviv.

On Tuesday, two pilots aboard another Super Hornet, again on the Truman, were forced to eject after their fighter jet failed to catch the steel cable on the carrier deck, sending the plane into the Red Sea.

By then, Mr. Trump had decided to declare the operation a success.

Houthi officials and their supporters swiftly declared victory, too, spreading a social media hashtag that read “Yemen defeats America.”

Ismaeel Naar contributed reporting from Dubai, United Arab Emirates.