Kirstjen Nielsen's departure as Homeland Security chief comes amid Trump's increasingly harsh border crackdown

Getty Images/Chip SomodevillaHomeland Security Secretary Kirstjen Nielsen speaks during a meeting of the Federal Commission on School Safety in the Indian Treaty Room in the Eisenhower Executive Office Building August 16, 2018 in Washington, DC.
  • Homeland Security Secretary Kirstjen Nielsen resigned on Sunday, ending a short but rocky tenure marred by controversy over President Donald Trump’s increasingly harsh immigration policies.
  • Her departure is the latest in a series of brash actions from the White House to stem the flow of Central American migrants that are crossing the US-Mexico border each month.
  • In recent weeks, Trump has withdrawn his nomination for Immigration and Customs Enforcement director, threatened to close the US-Mexico border, and vowed to cut off aid to Central American countries.
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The resignation of Homeland Security Secretary Kirstjen Nielsen on Sunday ended a short but rocky tenure marred by controversy and an increasingly volatile situation at the US-Mexico border that has enraged President Donald Trump for months.

Nielsen, who is best known as the face of the controversial “zero tolerance” border policy, was vilified by the president’s critics and supporters alike throughout her roughly 16 months on the job.

She was heavily criticised for defending what some saw as the cruelest part of the Trump administration’s legacy: forcibly separating thousands of migrant children from their parents, then repeatedly denying that the government had the policy in place.

Read more: Kirstjen Nielsen is out as Homeland Security Secretary

At the same time, she drew endless scorn from Trump and his fellow immigration hardliners over her inability to stem the flow of tens of thousands of Central American migrants arriving and seeking asylum at the US-Mexico border each month.

Though Nielsen tweeted out her full resignation letter Sunday evening, she had not intended to resign before she met with Trump earlier that day, The Washington Post reported. During their discussion, she was reportedly forced to step down.

In recent weeks, Trump’s rage over the border crossings has boiled over, as monthly apprehensions have reached their highest levels in more than a decade. Trump has long been fixated on the apprehension numbers – which indicate roughly how many people are crossing the border illegally – and has used them to gauge the success of his immigration agenda.

Skyrocketing border arrests have pushed Trump to a boiling point

EL PASO, TX - MARCH 28: Migrants awaiting processing are held in temporary fencing underneath the Paso Del Norte Bridge on March 28, 2019 in El Paso, Texas. U.S. Customs and Border Protection has temporarily closed all highway checkpoints along the 268-mile stretch of border in the El Paso sector to try to stem a surge in illegal entry. (Photo by Christ Chavez/Getty Images)Christ Chavez/Getty ImagesMigrants awaiting processing in El Paso, Texas.

Though the first year of Trump’s presidency yielded some of the lowest border apprehension numbers in decades, at one point sinking as low as just 16,000 apprehensions in April 2017, those numbers climbed throughout 2018 and exploded in the early months of 2019.

The embattled Customs and Border Protection agency is anticipated to have arrested 100,000 migrants in March 2019, according to The Washington Post, though final data has not yet been released.

What’s next for the Department of Homeland Security after Nielsen’s ouster is still unclear, but Trump’s moves of late have indicated an increasingly extreme and aggressive approach to preventing Central American migration and cracking down on rising border crossing levels.

Read more: 4 reasons the number of families crossing the US-Mexico border illegally is soaring, and how Trump may have made the problem worse

In just the last several weeks, Trump has lost his Homeland Security chief, withdrawn his nominee for Immigration and Customs Enforcement director to find someone “tougher,” vowed to cut off aid to the impoverished Central American countries from which a surge of migrants are fleeing, and even threatened to close down the entire US-Mexico border.

Earlier this year, Trump even declared a national emergency in an effort to secure funds for his long-promised border wall, though his declaration was challenged by both Congress and the courts.

“Country is FULL! System has been broken for many years. Democrats in Congress must agree to fix loopholes – No Open Border (Crimes & Drugs). Will Close Southern Border If necessary,” Trump tweeted Sunday evening after announcing Nielsen was leaving. “Mexico must apprehend all illegals and not let them make the long march up to the United States, or we will have no other choice than to Close the Border and/or institute Tariffs. Our Country is FULL!”

An immigration hawk takes the reins

Stephen MillerChip Somodevilla/Getty ImagesStephen Miller talks to reporters about President Donald Trump’s immigration system in December 2017.

Though Trump has backed away from his threats to close the border immediately, he has reportedly given a much freer rein to one of the staunchest immigration hardliners remaining in the White House: Stephen Miller.

Trump has now given Miller control over all immigration and border affairs, The Washington Post reportedFriday, citing several administration officials. The Post reported that Miller was behind Trump’s decision to withdraw the nomination of Acting ICE Director Ronald Vitiello. He also bemoaned Nielsen’s ineffectiveness to Trump, The New York Times reported.

Trump’s fixation on the border has even reportedly veered into the realm of impossible – or illegal – solutions.

Trump reportedly told Border Patrol agents on Friday that he wanted them to prevent migrants from crossing, CNN reported, citing a senior administration official. He also took to phoning Nielsen early in the mornings to demand she block all migrants from seeking asylum, The Times reported. Such a move would be illegal, as US law permits migrants to request asylum upon reaching US soil.

Nielsen “believed the situation was becoming untenable with the President becoming increasingly unhinged about the border crisis and making unreasonable and even impossible requests,” the senior administration official told CNN.

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