Why did Trump fire Kristi Noem as DHS secretary; who is Markwayne Mullin?

Noem will serve as special envoy for the Shield of the Americas, while Trump said Markwayne Mullin will lead the Department of Homeland Security.

United States President Donald Trump has announced that Kristi Noem will be replaced as secretary of the Department of Homeland Security (DHS), marking the first major change to his cabinet since his re-election.

Noem, who has overseen Trump’s controversial immigration crackdown, will instead serve as a special envoy for the Shield of the Americas, a newly created security initiative.

Her removal follows a tense, two-day congressional hearing on Capitol Hill, during which Noem faced a rare, united front of bipartisan hostility.

Trump has nominated Senator Markwayne Mullin to replace her. The change is expected to take effect on March 31.

Here is what we know:

Who is Kristi Noem?

Kristi Noem, 54, was the former Republican governor of South Dakota and recently served as the Secretary of Homeland Security in Trump’s administration.

In that role, she oversaw some of Trump’s key campaign priorities, including efforts to tighten security along the US-Mexico border and accelerate deportations of undocumented immigrants.

Her tenure was marked by high-profile immigration enforcement operations that were often publicised on social media, with Noem at times accompanying federal agents during arrests.

During this sweeping immigration crackdown across the US, two US citizens, Alex Pretti and Renee Good, were fatally shot by federal agents in Minneapolis earlier this year.

Noem also supervised the Federal Emergency Management Agency (FEMA) and its disaster response operations.

What has Trump announced?

In a post on his Truth Social account, Trump wrote that he was removing Noem from her position.

Despite the move, he praised her tenure, saying she “has served us well, and has had numerous and spectacular results (especially on the Border!)”.

Trump added that Noem would be reassigned to a newly created role as special envoy for the “Shield of the Americas”, a security initiative focused on the Western Hemisphere.

To replace her, Trump said he would nominate Republican Senator Markwayne Mullin of Oklahoma, whom he described as a “MAGA warrior”, to lead the Homeland Security Department.

The announcement came following controversy over a $220m border security advertising campaign featuring Noem on horseback. After Noem told Congress that Trump had approved the campaign, Trump denied involvement.

In a phone interview with the Reuters news agency, he said: “I never knew anything about it.”

What led to Trump’s reassignment of Noem?

Trump’s decision to reassign Noem followed a two-day congressional hearing on Capitol Hill, during which the Homeland Security Secretary faced questioning about her actions from members of both parties.

Reporting from Washington, DC, Al Jazeera’s Alan Fisher said Noem was “destroyed under questioning”, citing a series of controversies that made her continued leadership difficult.

Some of those include:

Minneapolis shootings:

Noem faced severe backlash over the deaths of two US citizen protesters, Renee Good and Alex Pretti, who were fatally shot by federal agents as immigration enforcement operations were under way in Minneapolis earlier this year and whose deaths had prompted nationwide protests.

Critics of the operation accused the administration of using excessive force and demanded an independent investigation.

Lawmakers also accused Noem of running a “smear campaign” by labelling the deceased as “domestic terrorists” in the wake of the killings, and criticised her for barring local investigators from the crime scenes.

“Republicans and Democrats were querying her handling of what happened in Minnesota, the death of two American citizens that she described initially as domestic terrorists, which proved to be untrue,” Fisher reported.

Controversial $220m advertisement campaign:

Noem was grilled about a roughly $220m border security advertising campaign that prominently featured her, including promotional footage of her on horseback near Mount Rushmore.

The contracts for the campaign drew criticism after they were awarded to firms with Republican political ties, including a subcontractor linked to people close to Noem. During congressional hearings, Noem said Trump had approved the campaign, but the president later told Reuters he “never knew anything about it”.

Kristi Noem is out at DHS. Here's a TV commercial of her on a horse, filmed five months ago at Mount Rushmore, for an ad campaign that cost more than $200 million pic.twitter.com/U1RtvlYc4w

— Drew Harwell (@drewharwell) March 5, 2026

FEMA mismanagement and disaster response:

Both Democrats and Republicans criticised Noem’s handling of emergency responses, such as the deadly Texas floods in July 2025 and Hurricane Helene in 2024.

Critics said her management style slowed some disaster response funding and reimbursements to states.

What is The Shield of the Americas?

The Shield of the Americas is a new US national security initiative focused on the Western Hemisphere, which Trump has established.

The initiative reflects Trump’s push to expand US security operations across the Western Hemisphere, including greater military and intelligence deployments, and is based on the Monroe Doctrine on “spheres of influence”, now dubbed the “Donroe Doctrine“.

The programme aims to dismantle cartels, combat drug trafficking and counter Chinese influence in Latin America.

On Thursday, Noem said the goal of the newfound summit is to “promote freedom, security and prosperity in our region”. Part of that includes partnering with 12 other countries to “address criminal narcoterrorist gangs and cartels and counter illegal and mass migration”.

Who is Markwayne Mullin?

Senator Mullin, 48, is one of Trump’s fiercest supporters on Capitol Hill.

A former business owner and undefeated MMA fighter with a 5-0 professional record, Mullin served for a decade in the House of Representatives before moving to the Senate in 2023. Known for his “MAGA Warrior” persona, he has long acted as a key intermediary between the White House and congressional Republicans.

If confirmed, Mullin, a citizen of the Cherokee Nation, would be the first Native American to lead the DHS.

He describes himself on his website as “a successful business owner, working cow-calf rancher, and proud husband of 28 years to Mrs Christie Mullin”.

He has previously supported Homeland Security policy and the administration’s immigration crackdown.

“Obstructing federal law enforcement is a felony. Most Americans follow ICE instructions without thinking twice,” Mullin said on social media following the death of Pretti.

Al Jazeera’s Fisher said the administration expects Mullin to be a “better administrator” than his predecessor.

“Even though Kristi Noem is a former governor, the White House didn’t feel she was running the organisation properly,” Fisher noted. “They feel they need someone with the experience of navigating the federal machine, and they believe Mullin is that person.”

While President Trump has announced that the official handover will take place on March 31, the transition is not as simple.

“[Trump] doesn’t just get to do that,” Fisher said, because DHS secretary is a Senate-approved position.

“So he has got to go through a Senate hearing with a committee, chaired by someone who described him as a snake,” Fisher reported.

“There are Democrats who want to make sure that Mullen will talk about how to change the way ICE operates; if he doesn’t deliver, they might not vote for him,” he added.

The Cherokee Nation released a statement Thursday, calling the nomination “historic” and noting that Mullin is both a senator from Oklahoma and a citizen of the Cherokee Nation.