Elon Musk’s time in the Trump administration is coming to an end after a tempestuous 129 days in which the world’s richest man took an axe to government spending – stirring ample controversy along the way.

Earlier this week, the South African-born billionaire, on his social media platform, X, thanked President Trump for his time at the Department of Government Efficiency, or Doge.

Trump announced he will host a news conference in the Oval Office on Friday with Musk, writing: “This will be his last day, but not really, because he will, always, be with us, helping all the way.”

While Musk’s time in government lasted little more than four months, his work with Doge upended the federal government and had an impact not just in the halls of power in Washington – but around the world.

Let’s take a look at some of the ways Musk has left a mark.

Musk took a job with the Trump White House with one mission: to cut spending from the government as much as possible.

He began with an initial target of “at least $2 trillion”, which then shifted to $1tn and ultimately $150bn.

To date, Doge claims to have saved $175bn through a combination of asset sales, lease and grant cancellations, “fraud and improper payment deletion”, regulatory savings and a 260,000-person reduction from the 2.3 million-strong federal workforce.

A BBC analysis of those figures, however, found that evidence is sometimes lacking.

This mission has at times caused both chaos and controversy, including some instances in which federal judges halted mass firings and ordered employees reinstated.

In other instances, the administration has been forced to backtrack on firings.

In one notable instance in February, the administration stopped the firing of hundreds of federal employees working at the National Nuclear Security Administration, including some with sensitive jobs related to the US nuclear arsenal.

Musk himself repeatedly acknowledged that mass firings would inevitably include mistakes.

“We will make mistakes,” he said in February, after his department mistook a region of Mozambique for Hamas-controlled Gaza while cutting an aid programme. “But we’ll act quickly to correct any mistakes.”

Doge’s efforts to access data also garnered controversy, particularly the department’s push for access to sensitive treasury department systems that control the private information of millions of Americans.

Polls show that cuts to government spending remain popular with many Americans – even if Musk’s personal popularity has waned.

The presence of Musk – an unelected “special government employee” with companies that count the US government as customers – in Trump’s White House has also raised eyebrows, prompting questions about potential conflicts of interest.

His corporate empire includes large companies that do business with US and foreign governments. SpaceX has $22 billion in US government contracts, according to the company’s chief executive.

Some Democrats also accused Musk of taking advantage of his position to drum up business abroad for his satellite internet services firm, Starlink.

The White House was accused of helping Musk’s businesses by showcasing vehicles made by Tesla – his embattled car company – on the White House lawn in March.

Musk and Trump have both shrugged off any suggestion that his work with the government is conflicted or ethically problematic.

Around the world, Musk’s work with Doge was most felt after the vast majority – over 80% – of the US Agency for International Development’s (USAID’s) programmes were eliminated following a six-week review by Doge. The rest were absorbed by the State Department.

The Musk and Doge-led cuts formed part of a wider effort by the Trump administration to bring overseas spending closer in line with its “America First” approach.

The cuts to the agency – tasked with work such as famine detection, vaccinations and food aid in conflict areas – quickly had an impact on projects including communal kitchens in war-torn Sudan, scholarships for young Afghan women who fled the Taliban and clinics for transgender people in India.

USAID also was a crucial instrument of US “soft power” around the world, leading some detractors pointing to its elimination as a sign of waning American influence on the global stage.

While Musk – and Trump – have for years been accused by detractors of spreading baseless conspiracy theories, Musk’s presence in the White House starkly highlighted how misinformation has crept into discourse at the highest levels of the US government.

For example, Musk spread an unfounded internet theory that US gold reserves had quietly been stolen from Fort Knox in Kentucky. At one point, he floated the idea of livestreaming a visit there to ensure the gold was secured.

More recently, Musk spread widely discredited rumours that the white Afrikaner population of South Africa is facing “genocide” in their home country.

Those rumours found their way into the Oval Office earlier in May, when a meeting aimed at soothing tensions between the US and South Africa took a drastic twist after Trump presented South African President Cyril Ramaphosa with videos and articles he said were evidence of crimes against Afrikaners.

Musk’s work in government also showed that, despite public pledges of unity, there are tensions within the “Trump 2.0” administration.

While Trump publicly – and repeatedly – backed the work of Musk and Doge, Musk’s tenure was marked by reports of tension between him and members of the cabinet who felt Doge cuts were impacting their agencies.

“They have a lot of respect for Elon and that he’s doing this, and some disagree a little bit,” Trump acknowledged in a February cabinet meeting. “If they aren’t, I want them to speak up.”

At one point, he was asked whether any cabinet members had expressed dissatisfaction with Musk and turned to the room to ask them. No one spoke.

The announcement of Musk’s departure also came the same day that CBS – the BBC’s US partner – publicised part of an interview during which Musk said he was “disappointed” by Trump’s “big, beautiful” budget bill. The bill includes multi-trillion dollar tax breaks and a pledge to increase defence spending.

Musk said the bill “undermines” the work of Doge to cut spending – reflecting larger tensions within the Republican Party over the path forward.