Former Vice President Mike Pence tore into Donald Trump and pointed to isolationism in the Republican Party as complicit in the sweeping Hamas attack on Israel, decrying American “retreat on the world stage.”

In a scathing rebuke, Pence faulted “voices of appeasement like Donald Trump, Vivek Ramaswamy and Ron DeSantis that I believe have run contrary to the tradition in our party that America is the leader of the free world.”

Pence’s comments in Iowa represented the first ripple in the Republican primary from the violence that erupted on Saturday — and effectively threw down a challenge to Republicans he said have “embraced the language of isolationism and appeasement.”

The role of the United States in maintaining global security is one of the most important points of friction between the Republican presidential candidates — one that could now erupt in a new way because of the violence in Israel. Pence’s criticism of Trump was uncharacteristically pointed. But it was even more remarkable for the break it represented in their previously lockstep approach to Israel. Once a signature priority of the Trump-Pence administration, the U.S.-Israel relationship Saturday was suddenly becoming a wedge issue between them.

Faulting President Joe Biden for “projecting weakness on the world stage,” Pence also pointed an accusatory finger rightward at an event here near the Nebraska border.

“This is also what happens when you have leaders in the Republican Party signaling retreat on the world stage,” Pence said.

When he added the Reaganesque line that “it’s time to get back to peace through strength," the candidate polling in single digits nationally received an uncharacteristically sustained round of applause.

“Backing our allies and doing things in their neighborhood so it doesn’t come to the United States is important,” Larry Winum, a 59-year-old banker who had come to hear Pence at a local senior center, said.

Pence has made engagement with the world and backing Ukraine in the nation’s conflict with Russia a hallmark of his campaign, earlier this year becoming the first GOP presidential candidate to meet with Ukrainian President Volodymyr Zelenskyy. It’s a message that’s not universally embraced in his own party: Even his own brother, Rep. Greg Pence of Indiana, voted recently against an appropriations bill aimed at providing further aid to Ukraine.

Several underdog candidates, including Pence and Nikki Haley, the former ambassador to the United Nations, have castigated factions on the right that want to pull back American involvement in overseas conflicts like the war in Ukraine.

Those more isolationist constituencies have found vocal champions in Trump and other candidates like the biotech entrepreneur Ramaswamy, who has taken a dismissive view of Ukraine and other traditional American priorities like the security of Taiwan.

Most Republican candidates, however, stuck to a narrow message on Saturday of support for Israel and criticism of the Biden administration. Trump, the dominant frontrunner in the race, spent part of the morning posting social-media messages on an entirely unrelated matter — his legal battle with New York Attorney General Tish James.

There is a history of foreign security crises shaping American presidential primaries. In 2007, the assassination of Benazir Bhutto in Pakistan helped refocus the Republican nominating contest on security issues in a way that helped John McCain resurrect his candidacy. Four years ago, the killing of the Iranian military leader Qasem Soleimani by the Trump administration pushed Democratic candidates to address national security concerns in a campaign largely focused on domestic economic and cultural debates.

On Saturday, Trump praised his previous administration’s policies on Israel while bashing the current White House.

“These Hamas attacks are a disgrace and Israel has every right to defend itself with overwhelming force,” Trump said in a statement released by his campaign. “Sadly, American taxpayer dollars helped fund these attacks, which many reports are saying came from the Biden Administration. We brought so much peace to the Middle East through the Abraham Accords, only to see Biden whittle it away at a far more rapid pace than anyone thought possible. Here we go again.”

Haley said that Hamas had “declared war on Israel” on the 50th anniversary of the Yom Kippur War, calling the group a “bloodthirsty terrorist organization backed by Iran and determined to kill as many innocent lives as possible.”

DeSantis, the Florida governor, called for “a swift and lethal response” and said that “America must stand with Israel.”

“The dastardly terrorist attacks perpetrated against innocent Israeli civilians by Iran-backed terror group Hamas deserve a swift and lethal response,” the GOP presidential candidate — and longtime ally to Israel — said in a social media post, followed by a video of him speaking directly to camera.

A spokesperson for Ramaswamy’s campaign, Tricia McLaughlin, issued a statement on his behalf.

“We stand with Israel and are appalled by these attacks,” McLaughlin said. “Shooting civilians and kidnapping children are war crimes. Israel’s right to exist and defend itself must never be doubted. Hamas and Hezbollah terrorists cannot be allowed to prevail.”

Chris Christie wrote in a social media post: "Biden’s appeasement of Israel’s enemies has invited this war against Israel. ... This terrorism is funded by Biden’s idiotic release of $6 billion to the Iranians."

South Carolina Sen. Tim Scott also blamed the Biden administration. “The truth is though, Joe Biden funded these attacks on Israel,” he said.

But NSC spokesperson Adrienne Watson disputed those assertions in a social media post.

"I can't comment on 2024 because of the Hatch Act. But I can clarify the facts: Not a single cent from these funds has been spent, and when it is spent, it can only be spent on things like food and medicine for the Iranian people," she wrote.

White House Deputy Press Secretary Andrew Bates further called the allegations "a shameful lie" in a post on X.

And State Dept. spokesperson Matthew Miller also hit back, writing: "Let's be clear: the deal to bring U.S. citizens home from Iran has nothing to do with the horrific attack on Israel. Not a penny has been spent, and when it is, it can only go for humanitarian needs like food and medicine. Anything to the contrary is false."