During his first term as president, tested the limits of how he could use the military to achieve policy goals. If given a second term, the Republican and his allies are preparing to go much further, reimagining the military as an .

He has pledged to recall thousands of American troops from overseas and station them at the U.S. border with Mexico. He has explored using and confronting civil unrest. He has talked of weeding out military officers who are ideologically opposed to him.

Trump鈥檚 vision amounts to a potentially dramatic shift in the role of the military in U.S. society, carrying grave implications for both the country鈥檚 place in the world and the restraints that have traditionally been placed on domestic use of the military.

As Trump鈥檚 campaign heads into its final stretch against Democratic Vice President Kamala Harris, he is promising forceful action against immigrants who do not have permanent legal status. on Friday, the Republican described the city of Aurora as a 鈥渨ar zone鈥� controlled by Venezuelan gangs, even though authorities say that was , and the area is safe again.

鈥淚 will rescue Aurora and every town that has been invaded and conquered,鈥� Trump said at the rally. 鈥淲e will put these vicious and bloodthirsty criminals in jail or kick them out of our country.鈥�

In an interview aired Sunday on Fox News Channel, Trump was asked about the potential of 鈥渙utside agitators鈥� disrupting Election Day and he then pivoted to what he called 鈥渢he enemy from within.鈥�

鈥淚 think the bigger problem is the enemy from within,鈥� Trump said. He added: 鈥淲e have some very bad people. We have some sick people, radical left lunatics. And I think they鈥檙e the big 鈥� and it should be very easily handled by, if necessary, by National Guard, or if really necessary, by the military, because they can鈥檛 let that happen.鈥�

Trump has repeatedly invoked the phrase 鈥渆nemy from within鈥� in recent speeches. On Saturday, he used it to refer to Rep. Adam Schiff, D-Calif., a prominent Trump critic who oversaw the congressional investigation that led to Trump鈥檚 first impeachment. Schiff is now running for the Senate.

The former president and his advisers are developing plans to shift the military鈥檚 priorities and resources, even at a time when wars are raging in Europe and the Middle East. Trump鈥檚 top priority in his platform, known as , is to implement hardline measures at the U.S.-Mexico border by 鈥渕oving thousands of troops currently stationed overseas鈥� to that border. He is also pledging to 鈥渄eclare war鈥� on cartels and deploy the Navy in a blockade that would board and inspect ships for fentanyl.

Trump also has said he will use the National Guard and possibly the military as part of the operation to deport millions of immigrants who do not have permanent legal status.

While Trump鈥檚 campaign declined to discuss the details of those plans, including how many troops he would shift from overseas assignments to the border, his allies are not shy about casting the operation as a sweeping mission that would use the most powerful tools of the federal government in new and dramatic ways.

鈥淭here could be an alliance of the Justice Department, Homeland Security and the Department of Defense. Those three departments have to be coordinated in a way that maybe has never been done before,鈥� said Ron Vitiello, who worked as the acting director of Immigrations and Customs Enforcement under Trump.

While both Democratic and Republican presidential administrations have long used military resources at the border, the plans would be a striking escalation of the military鈥檚 involvement in domestic policy.

Advocates for human rights and civil liberties have grown alarmed.

鈥淭hey are promising to use the military to do mass raids of American families at a scale that harkens back to some of the worst things our country has done,鈥� said Todd Schulte, president of FWD.us, an immigration advocacy organization.

In Congress, which has the power to restrict the use of military force through funding and other authorizations, Republicans are largely on board with Trump鈥檚 plans.

鈥淭he reason I support Donald Trump is he will secure the border on Day 1. Now that could be misinterpreted as being a dictator. No, he鈥檚 got to secure the border,鈥� said Rep. Joe Wilson, R-S.C., a member of the House Armed Services Committee.

Many Republicans argue that reflects reality and points to the need for military action.

鈥淭here is a case that this is an invasion,鈥� said North Carolina Sen. Ted Budd, a Republican on the Senate Armed Services Committee. 鈥淵ou look at 10 million people, many of which are not here for a better future, and, unfortunately, it鈥檚 made it necessary. This is a problem that the Biden administration and Harris administration have created.鈥�

Still, Trump鈥檚 plans to move military assets from abroad could further inflame tension within the GOP between those hawkish on foreign policy and Republicans who promote Trump鈥檚 brand of 鈥淎merica First鈥� isolationism.

Republican Rep. Mike Rogers of Alabama, chairman of the House Armed Services Committee, insisted Trump would not move active-duty troops to the border, even though Trump鈥檚 platform clearly states he would.

In the Senate, where more traditional Republicans still hold sway, Mississippi Sen. Roger Wicker, the top Republican on the Armed Services Committee, issued a statement encouraging the Department of Defense to assist with border security, but adding that the effort 鈥渘eeds to be led by the Department of Homeland Security.鈥�

Trump鈥檚 designs for the military may not stop at the border.

As Trump completes a campaign marked by serious threats to his life, his aides already made an to transport him amid growing concerns over .

During his first term while riots and protests against police brutality roiled the nation, Trump also military personnel. Top military officers, such as then- , including issuing a memo that stressed that every member of the military 鈥渟wears an oath to support and defend the Constitution and the values embedded within it.鈥�

Trump鈥檚 potential actions would likely require him to invoke wartime or emergency powers, such as carrying out , a 1798 law, or , an 1807 law that allows a president to deploy the military domestically and against U.S. citizens. It was last used by President George H.W. Bush in 1992 during rioting in Los Angeles after police officers beat the Black motorist Rodney King.

Ahead of a potential second term for Trump, Democrats in Congress tried to update presidential powers like the Insurrection Act but found little success.

That鈥檚 left them instead issuing dire warnings that Trump now has fewer guardrails on how he could use the military. He has shown an ability to bend institutions to his goals, from a Supreme Court willing to reconsider long-standing interpretations of presidential powers to a military scrubbed of officers and leaders likely to push back on his plans.

Sen. Richard Blumenthal, D-Conn., who introduced legislation to update the Insurrection Act, said the plans 鈥渋lluminate Donald Trump鈥檚 total misunderstanding of the United States military as a force for national defense, not for his personal preferences to demagogue an issue.鈥�

But Rep. Dan Crenshaw, R-Texas, underscored how many in his party have grown comfortable with deploying the military to confront illegal immigration and drug trafficking.

鈥淲hatever fixes the border, I think we鈥檙e OK with,鈥� he said.