US President Donald Trump's tariffs haven't only affected global markets and decades-old geopolitical alliances.
They've also caused a rift between two of his top advisers.
In the days since Mr Trump announced sweeping tariffs, long-time trade adviser Peter Navarro and White House DOGE office affiliate Elon Musk have been locked in a public feud.
Navarro is credited with having influence over Trump's wide-ranging tariff plans.
While Mr Musk has posted online about the virtues of free trade.
Who is Peter Navarro?
Navarro, 75, is an American economist who was tapped by Mr Trump in December as his senior counsellor for trade and manufacturing.
He served in Mr Trump's first administration where he ran a newly created National Trade Council and then the Office of Trade and Manufacturing Policy.
He graduated from Tufts University and later Harvard University with a doctorate degree in economics.
Navarro made history as the first former White House official to be imprisoned for a contempt of Congress conviction.
He was sentenced to four months in a low security facility in Miami for his refusal to comply with a subpoena from the House Select Committee that investigated the January 6, 2021, US Capitol attack.
Hours after his release from prison, Navarro spoke at the Republic National Convention in Milwaukee where he was met with a long standing ovation from the crowd.
Amid chants of 'fight, fight, fight,' he said: "I've got a very simple message for you: If they can come for me, if they can come for Donald Trump, be careful, they will come for you."
Navarro's prison consultant, Sam Mangel, told US publication ABC News the adviser "worked in the prison library and had no issues with other inmates or staff".
Fictional alter ego scandal
In 2019, Navarro was busted for repeatedly quoting a Harvard-educated economist in books that did not actually exist.
Out of Navarro's 13 published books, expert Ron Vara has appeared as a voice of economic wisdom in six of them, including in his 2011 book Death By China.
But it wasn't until a professor at the Australian National University did some further investigating that she found out Vara was a made-up alter ego.
In fact, the name Ron Vara is an anagram of Navarro's name.
ANU scholar Tessa Morris-Suzuki told SBS back in 2019 that she made the discovery during her research to write a blog piece on anti-China rhetoric.
"It was really, entirely by accident," Ms Morris-Suzuki said.
She said some of Vara's quotes published in one of the books were "quite concerning" so she Googled his name and even phoned Harvard to confirm he was a student there.
Her hunch was confirmed after she was told the university had no record of a Ron Vara ever attending.
Navarro acknowledged the fabrication, calling it a "whimsical device" when he spoke to the Chronicle of Higher Education.
"It's a pen name…for opinion and purely entertainment value, not as a source of fact," he said at the time.
He even downplayed the scandal saying it was "refreshing somebody finally figured out an inside joke that has been hiding in plain sight".
Jared Mondschein, director of research at the United States Studies Centre, told the ABC that Navarro used the anagram as a way to show "someone who agreed with his agenda".
What impact is he having on tariffs?
Navarro is considered one of the most ardent supporters of keeping tariffs in place for the long term.
His plans for trade were the basis for half a chapter of Project 2025, a policy guide published by conservative think tank Heritage Foundation.
He urged that the next Republican president take aim at "those countries that have relatively large trade deficits with the US and apply relatively high tariffs".
Specifically, China, India, Thailand, Taiwan, Vietnam, Malaysia, Japan and the European Union (EU).
When Trump unveiled his 'Liberation Day' tariffs, the eight trading partners Navarro called out in Project 2025 were all listed as among those set to face relatively high levies.
For example, 46 per cent for Vietnam to 20 per cent for the EU.
In the chapter, one policy recommended by Navarro includes expanding tariffs on China to "block out" Chinese-made goods.
And ever since Mr Trump introduced the tariffs on April 2, a trade war between the two countries has escalated.
The US president has threatened China with a 104 per cent tariff if Beijing doesn't withdraw its retaliatory 34 per cent levy on American goods.
Mr Mondschein says Navarro's approach has been well known for decades.
"His approach is by no means conventional," Mr Mondschein said.
"He has Harvard credentials but I don't know many Harvard trained economists who agree with him..."
But Mr Mondschein believes it's a mistake to think the tariff policy is just from Navarro himself.
"I think this is Donald Trump.
"He's not consistent in many things in his life.
"But he is consistent on trade more than anything else.
"Yes, Navarro does provide Trump with more experience in this trade area, but even without him, Trump would have gone ahead."
The tariff policy implemented by the president is intended to revive US manufacturing and shore up national security but has hammered markets and thrown global supply chains into uncertainty.
Why is he fighting with Elon Musk?
The spat between Mr Musk and Navarro is the most public rift between members of Mr Trump's inner circle.
And it's played out publicly on social media over the president's tariff regime.
The tariffs revealed on 'Liberation Day' were seen as a policy win for Navarro, who has advocated for trade measures in the hope of helping boost domestic manufacturing.
Shortly after, Mr Musk took to his social media platform X posting that a "PhD in econ from Harvard is a bad thing, not a good thing," a reference to Navarro's degree.
In a subsequent interview with US broadcaster CNBC, Navarro said Mr Musk's comments on "zero tariffs" was unsurprising given his role as a "car person".
"When it comes to tariffs and trade, we all understand in the White House — and the American people understand — that Elon is a car manufacturer, but he's not a car manufacturer. He's a car assembler," Navarro said.
"He wants the cheap foreign parts," he added.
In retaliation, Mr Musk called Navarro "truly a moron" and mocked the trade adviser for in the past citing the work of 'Ron Vara'.
When asked about the feud in a briefing on Tuesday (local time), White House press secretary Karoline Leavitt said:
"Look, these are obviously two individuals who have very different views on trade and on tariffs," she said.
"Boys will be boys, and we will let their public sparring continue."
But in-fighting isn't exactly a novel phenomenon within the Trump administration.
"In Trump's first term, there was even more fighting and if anything it's surprising it took this long for such fights to be out in the open," Mr Mondschein said.
