Jeb Bush struggled for several days earlier this year to say whether he would have authorized the Iraq war, a blunder that exposed his difficulty in talking about what many Americans consider the biggest failure of George W. Bush’s presidency.

On Tuesday night, Jeb Bush, who is seeking the Republican presidential nomination, attacked President Obama and former secretary of state Hillary Rodham Clinton for their “premature” decision to withdraw U.S. forces from Iraq — a move he describes as a “fatal error.”

“It was a case of blind haste to get out, and to call the tragic consequences somebody else’s problem,” he said. “Rushing away from danger can be every bit as unwise as rushing into danger, and the costs have been grievous.”

Bush’s speech at the Ronald Reagan Presidential Library — the most specific foreign policy address by a GOP candidate this cycle — included his first detailed set of ideas on how to combat the rise of the Islamic State terrorist group, also known as ISIS, in Iraq and Syria. But it also marked a new effort to confront Clinton, a Democratic presidential candidate, and make his mark on Middle Eastern affairs. The move poses a risk by implicitly linking him to the unpopular policies of his brother.

Unmentioned by Bush, for example, was that George W. Bush started the process of withdrawing U.S. forces from Iraq. Once in office, Obama sought to ensure that U.S. troops would continue to have legal immunity while in the country. But the Iraqi government refused, leading to the exit of all but residual U.S. forces by December 2011.

Former Florida governor Jeb Bush gives a key foreign policy speech at the Ronald Reagan Presidential Library in Simi Valley, Calif. (Charles Ommanney/The Washington Post)

Jeb Bush’s comments come as Clinton has intensified her attacks on him, as many Democrats privately think he will ultimately become the GOP nominee despite the current popularity of Donald Trump. She has targeted Bush’s stance on abortion rights, federal funding for women’s health research, taxes and U.S.-Cuba relations.

Relishing the attention, Bush’s campaign has begun to strike back. On Monday, the rival camps traded barbs over Clinton’s $350 billion plan to make college affordable and relieve the burden of student debt for millions of Americans. Instead of press releases or television appearances, they mostly used Twitter to make their points.

He charged that Clinton allowed unrest in Iraq to intensify by not checking the rise of ISIS, which is occupying parts of the war-torn country and neighboring Syria.

“What we are facing in ISIS and its ideology is, to borrow a phrase, the focus of evil in the modern world,” Bush said. “And civilized nations everywhere, especially those with power, have a duty to oppose and defeat this enemy.”

Bush noted that ISIS is using Twitter, Facebook and Instagram “to add a veneer of glamor to their exploits” and suggested that the U.S. government should “work with the owners of the relevant companies, and give careful thought to how we address this problem.”

The Obama administration has pushed high-tech and social media firms with little success to block terrorist organizations from using their platforms.

He noted that about 3,500 U.S. ground troops are in Iraq and that “more may well be needed.” He endorsed deploying the troops to work more closely with Iraqi forces, including as forward air spotters to help identify air raid sites.

Attendees listen as former Florida governor Jeb Bush gives his speech. (Charles Ommanney/The Washington Post)

“We do not need, and our friends do not ask for, a major commitment of American combat forces,” he said. “But we do need to convey that we are serious, that we are determined to help local forces take back their country.”

In Syria, Bush called for a no-fly zone — “a critical strategic step” to block Syrian President Bashar al-Assad’s regime’s bombing of civilians and Iran from resupplying the Syrian government and Hezbollah fighters.

Bush’s remarks came nearly three months after he struggled for several days to explain whether he would have authorized the Iraq war based on intelligence that emerged after the conflict began. Ultimately, he said he would not have ordered U.S. forces to invade. But he remains a strong defender of the 2007 troop “surge” his brother ordered, believing that it helped American troops restore order to the country.

“So why was the success of the surge followed by a withdrawal from Iraq, leaving not even the residual force that commanders and the Joint Chiefs knew was necessary?” he said. “That premature withdrawal was the fatal error, creating the void that ISIS moved in to fill — and that Iran has exploited to the full as well.

“And where was Secretary of State Clinton in all of this?” he added. “Like the president himself, she had opposed the surge . . . then joined in claiming credit for its success . . . then stood by as that hard-won victory by American and allied forces was thrown away.”

 Clinton holds the record for the most countries visited by a secretary of state, at 112. But on Tuesday night, Bush noted that “in all her record-setting travels, she stopped by Iraq exactly once.”

In recent years, polls by The Washington Post and other news organizations have consistently shown that a majority of Americans think the Iraq war was not worth fighting, with Republicans slightly more supportive. Although George W. Bush’s popularity has improved in recent months, most Americans still hold him chiefly responsible for the war’s failures.

As a senator from New York, Clinton voted to authorize the Iraq war. As a presidential candidate in 2008, she called her support a mistake and blasted Bush’s handling of it. On Tuesday, her aides tried to connect the legacy of one Bush brother to the campaign of another.

“This is a pretty bold attempt to rewrite history and reassign responsibility,” said Jake Sullivan, a former State Department official and the Clinton campaign’s lead foreign policy adviser.

Responding to Bush’s charge that Clinton did not visit Iraq more often, Sullivan noted that she spoke frequently with Iraqi leaders, instructed deputies to hold weekly video conferences with U.S. Embassy personnel in Baghdad and briefed Obama on Iraq several times.

“The key issue is not how many times a plane touches down at the airport,” he said. “It’s how intensive and effective is the engagement that leads to progress.”

Karen DeYoung in Washington contributed to this report.