M. Zuhdi Jasser with McClatchy Newspapers,Tim Johnson

When President Barack Obama contemplated a military strike in Syria after its leader’s use of chemical weapons five years ago, the pugnacious former U.N. ambassador John Bolton argued against intervention.

“I don’t think it is in America’s interest,” Bolton said in a FOX interview in 2013. “I don’t think we should in effect take sides in the Syrian conflict.”

Yet for the last week, Bolton, President Donald Trump’s new national security adviser, has been pushing for a more aggressive approach to Syria, illustrating his views in the region have changed dramatically as he has become more alarmed about the rise of influence by Russia and Iran, key allies of Syrian President Bashar al-Assad.

“Ultimately, he views the Syrian crisis through the lens of Iran and Iran’s potential dominance in the region,” said Mark Groombridge, a former Bolton aide at the State Department whom he brought as an adviser in 2005 when he became ambassador.

When the United States — along with France and Britain — launched military strikes on sites designed to destroy Assad’s chemical weapons program in Syria on Friday, critics blamed Bolton.

The liberal group People’s Action described him as “John ‘Bomb ‘em all’ Bolton” in a fundraising appeal to supporters Saturday.

Bolton stood near Trump when he briefly addressed the nation about the strikes Friday night, periodically making notes on a yellow legal pad.

U.S. defense officials said the strikes could be repeated if Assad uses chemical weapons again.

But former colleagues say Bolton, now one of the most influential foreign policy voices in Trump’s administration, is focusing less on the use of chemical weapons than on broader geopolitical issues in the Middle East that have evolved in the past half-decade.

“We’re dealing with a very different situation now. Russia and Iran have saved the Assad regime,” said Nicholas Rostow, who served as a national security aide to George W. Bush and has long known and worked with Bolton. “Assad has showed a consistent willingness to ignore his commitment about chemical weapons and to use them.”

Rostow said there’s no conflict with what Bolton previously said about Syria and what he says now. “John is very smart,” he said. “He’ll think next steps.”

Bolton replaced H.R. McMaster on Monday as national security adviser, part of a series of White House staff changes in recent weeks. Trump also nominated CIA Director Mike Pompeo to be secretary of state after firing Rex Tillerson.

“He’s going to be much more hands on, much more managerial,” said Douglas H. Paal, a former staff member on the National Security Council under former presidents Ronald Reagan and George H.W. Bush and is now at the Carnegie Endowment for International Peace.

Bolton and Trump met regularly during the presidential transition and at the White House to discuss foreign policy. In the last week, he has been a constant presence at Syrian deliberations and was in the Oval Office when Trump called British Prime Minister Theresa May.

Jon Soltz, an Iraq War veteran and chairman of VoteVets, a group that opposes the wars in Iraq and Afghanistan, said it is “a clear indication of what many have warned” that with the hiring of Pompeo and Bolton Trump has assembled “a neocon war cabinet,” referring to the hawkish wing of conservatives known as neo-conservatives.

James Jeffrey, who served as U.S. ambassador to Iraq and Turkey and deputy national security adviser in the George W. Bush administration, said Bolton was wrong to say that the United States shouldn’t take sides in the civil war, but he said that was also before Russia got involved.

And then there was the politics. Bolton is political, Jeffrey said.

“Remember when Bolton made that comment, it was the Obama administration,” Jeffrey said. “So whatever the administration is announcing to do, as a pundit on the other side, you roll out all the arguments against it.”

Bolton’s next key test will be helping Trump decide next month whether to withdraw from the Iran nuclear deal, which he has long opposed. The 2015 agreement was designed to allow Iran to pursue a nuclear program but prevent it from producing a nuclear weapon.

Bolton, an advocate for the use of U.S. military might throughout his career, was one of the architects of Bush’s 2003 invasion of Iraq.

That’s why his views in 2013 on Syria were so surprising. “There’s very little to recommend either side to me, and I think the notion that a limited strike, which is what the president seems to be pursuing, will not create a deterrent effect with respect to either to Syria’s use of chemical weapons or, more seriously, Iran’s nuclear weapons program,” he told FOX.

“I don’t think what Bolton has said in the past on this is so relevant, frankly,” said Paul B. Stares, who worked on the Iraq Study Group and the U.S Institute of Peace, a federal institution that is involved in conflicts around the world. “People change their views, especially those who get read into new sensitive information. They can claim that, ‘I said that when I was ignorant of the facts or not briefed on the facts,’” said Stares, who is now at the Council of Foreign Relations.

Another Bolton ally said the situation in and around Syria has changed drastically in the years Bolton cautioned against a military strike.

“What’s changed in Syria is the significant influence of Iran, of Hezbollah and of Russia,” said Zuhdi Jasser, a Syrian-American who is founder of the American Islamic Forum for Democracy. “It is no longer a civil war … It is a regional proxy war in which the Shia radical Islamists based in Tehran are seeking to homogenize the crescent through Iraq, through Syria and into Lebanon.”

“This is a totally different calculus now,” said Jasser, who has frequently served on panels with Bolton, including Feb. 23 at the Conservative Political Action Conference, the nation’s largest annual gathering of conservatives.

Asked at the White House last week about his past views, Press Secretary Sarah Huckabee Sanders downplayed them. “The point of view that matters most here at the White House, as you well know, is the president’s,” she said.