He campaigned against involvement in foreign wars and promised to bring world peace, but President Trump is now grappling with involving the U.S. in an expanding war in the Middle East, and it has ignited a meltdown among his supporters.

Anti-war conservatives in the president’s base say Mr. Trump risks destroying his “America First” legacy if he inserts U.S. warplanes and their 30,000-pound “bunker buster” bombs into Israel’s effort to gut the Iranian regime and destroy the Islamic republic’s nuclear facilities.

Those warnings mounted Tuesday as Mr. Trump ramped up his support for Israel’s escalating assault. Since Friday, Israel has taken out top leaders, killed hundreds and destroyed nuclear and military sites in Iran.

As the Israeli bombardment expanded, Tehran’s ability to fight back appeared diminished. Fewer Iranian missiles were striking Israel.

The Israeli military said it had killed Iran’s senior military commander, Maj. Gen. Ali Shadmani. Iran did not immediately comment.

Israeli military spokesman Brig. Gen. Effie Defrin announced another wave of strikes Tuesday evening as explosions and anti-aircraft fire boomed throughout Tehran, shaking buildings across the capital. The Israeli military said its warplanes had targeted 12 missile launch sites and storage facilities.

Tehran residents fled their homes in droves, and the U.N. nuclear watchdog said for the first time that Israeli strikes on Iran’s main uranium-enrichment facility at Natanz had damaged its main underground section, not just an aboveground facility as previously acknowledged.

Mr. Trump, posting on his social media site, said he was not interested in a ceasefire but wants Iran’s “UNCONDITIONAL SURRENDER.”

The president suggested that the U.S. was teaming up with Israel in the onslaught. “We have complete and total control over the skies of Iran,” he posted on social media, adding that the U.S. “knows “exactly where the so-called ‘Supreme Leader’ is hiding.”

Mr. Trump said the U.S. won’t “take him out (kill!) at least for now.”

A U.S. strike on Iran is now on the table, Axios reported late Tuesday. The outlet also reported that Mr. Trump held another phone call with Israeli Prime Minister Benjamin Netanyahu.

A U.S. strike would likely be aimed at taking out Iran’s underground nuclear facilities, especially at Fordo and Natanz, using precision-guided bombs that can be delivered only by U.S.-made B-2 bombers and American pilots. Analysts say it’s the only weapon in the world capable of penetrating 200 feet underground before detonating and destroying the nuclear complexes.

The U.S. action could send some of Mr. Trump’s most ardent supporters into a meltdown and implode his base.

A central pledge of Mr. Trump’s 2024 campaign was keeping the U.S. out of another endless Middle East war.

Bitter MAGA followers protested on social media by posting clips of Mr. Trump making anti-war promises and criticizing his predecessors for costing thousands of U.S. lives and billions of dollars on foreign conflicts.

Five months after starting his second term, the president is sending U.S. Navy ships and military aircraft tankers to the region and threatening the Iranian government as it retaliates against Israel with waves of ballistic missile attacks.

“Our patience is wearing thin,” Mr. Trump said.

Because of the urgency of his decision, the president canceled his attendance at the Group of Seven summit in Alberta on Monday night and flew back to Washington. He arrived at the White House shortly after 5 a.m. Tuesday.

Mr. Trump convened his National Security Council in the highly secure, underground Situation Room at the White House to weigh the next steps. The group met for nearly an hour and a half.

As Mr. Trump pushed the U.S. to the brink of a military strike on Iran, allies said the president wasn’t at risk of violating a campaign pledge. They said he was sticking to his long-held commitment to prevent Iran, labeled a terrorist state, from obtaining a nuclear weapon. He has repeated that pledge dozens of times.

“I will stop Iran from getting nuclear weapons,” Mr. Trump said when he announced his first campaign for president a decade ago.

He withdrew the U.S. from a nuclear deal with Iran during his first term. He called it one-sided and argued that it merely delayed Iran’s path to developing a nuclear weapon.

In his second term, Mr. Trump has repeatedly called on Iran to abandon its nuclear ambitions. The U.S. was engaged in nuclear talks with Tehran last week when Israel struck its longtime enemy.

“Four presidents have promised to stop Iran from getting a nuclear bomb. Only Donald J. Trump will deliver on that promise,” said Sen. Lindsey Graham, South Carolina Republican.

Other supporters were confident that Mr. Trump would never lead the U.S. into a war.

“President Trump knows his base. Have some faith in his ability to handle this,” said Charlie Kirk, founder of Turning Point USA, which campaigned for Mr. Trump last year. “His whole life has led to this moment.”

Mr. Kirk was pivotal in generating votes for Mr. Trump among young voters, but he warned Tuesday that Mr. Trump’s base supported him “because he was the first president in my lifetime to not start a new war.”

He posted an online poll on X asking whether the U.S. should get involved “in Israel’s war against Iran.”

Of the nearly half a million people who responded to the poll, 90% said “No.”

Republican analysts said Mr. Trump’s actions in the coming days could define his legacy.

“The American people reelected President Trump, in part, because of his unique combination of toughness and shrewd negotiating skills, and this high-stakes moment will require both traits,” said Mark Bednar, who served as a top aide to House Speaker Kevin McCarthy.

Democrats blame the Middle East fighting on Mr. Trump’s foreign policy.

“This chaos is a direct result of Donald Trump’s erratic leadership and undermines the central premise of his candidacy,” said Daniel Pfeiffer, who served as a senior adviser to President Obama.

On Capitol Hill, Sen. Tim Kaine, Virginia Democrat, introduced a war powers resolution and planned to force a vote on it as soon as next Wednesday. Senate Majority Leader John Thune, South Dakota Republican, called the move premature.

The measure directs the president to terminate the use of U.S. armed forces for “hostilities” against Iran unless explicitly authorized by a congressional declaration of war or specific authorization for use of military force against Iran. It includes a caveat allowing the U.S. to defend itself from “imminent attack.”

Middle East Institute senior fellow Brian Katulis said Mr. Trump is on the brink of failing all his foreign policy goals, which include ending the war between Russia and Ukraine.

“It’s not just what he promised as a candidate. It’s the disarray in his foreign policy, not delivering on Russia when he put so much in his early weeks and months to focus on it,” Mr. Katulis said.

Vice President J.D. Vance, in a lengthy post on X, defended Mr. Trump’s consistent pledge to stop Iran from having a nuclear weapon as the Islamic republic continued its program to enrich uranium beyond what is needed for civilian use.

“He may decide he needs to take further action to end Iranian enrichment,” Mr. Vance said. “That decision ultimately belongs to the president. And of course, people are right to be worried about foreign entanglement after the last 25 years of idiotic foreign policy.”

Yet Mr. Vance said, “I believe the president has earned some trust on this issue. And having seen this up close and personal, I can assure you that he is only interested in using the American military to accomplish the American people’s goals. Whatever he does, that is his focus.”

• Mallory Wilson and Lindsey McPherson contributed to this article, which is based in part on wire service reports.

• Susan Ferrechio can be reached at sferrechio@washingtontimes.com.

• Jeff Mordock can be reached at jmordock@washingtontimes.com.