The decision to order the Department of Defense to deploy active duty military troops, as opposed to members of the National Guard, has been described as political posturing by defense experts.

election approaches, Trump has ramped up his rhetoric against the caravan and against undocumented immigrants generally. This week, Trump called for an end to birthright citizenship guaranteed by the U.S. Constitution, setting off a rift within his own party.

President Trump said Thursday that he hopes the military troops being deployed to the United States’ southwestern border will not have to fire upon any migrants attempting to enter the country through Mexico, but warned that if any rocks are thrown from across the border “we will consider that a firearm.”

“They want to throw rocks at our military, our military fights back,” Trump said. “I say, consider it a rifle.”

White House sources had told reporters that Trump would announce a new immigration policy aimed at restricting entry for asylum seekers at the southwest border in an address from the White House Thursday afternoon. But the president outlined no concrete policy changes, instead referring vaguely to plans for the construction of “massive cities of tents” to house migrants with pending asylum claims “for a long time if necessary.”

He pledged to end the “catch and release” practice of paroling refugees with credible asylum claims into the population. “We’re gonna catch, we’re not gonna release,” he said, claiming that just “3 percent” of asylum seekers return for court hearings on their claims. The actual number, according to Justice Department figures, is between 60 and 75 percent.

He said he planned to issue an executive order on the subject, but didn’t say what it would consist of.

For the most part, Trump simply amplified many of the same unsubstantiated claims that he’s been airing at rallies and on Twitter over the past two weeks about a caravan of mostly Honduran migrants slowly making its way through Mexico.

“It’s like an invasion,” Trump said, describing the thousands of migrants who, as of earlier this week, were still at least 1,000 miles away from the nearest U.S. point of entry, as a violent and imminent threat to the country.

“These are pretty tough people, and I don’t want them in our country. Women don’t want them in our country,” he said. “Women want security.”

Trump began focusing his attention on the so-called caravan last month, when a large group of migrants first departed the Honduran city of San Pedro de Sula, growing to more than 7,000 as it traveled through Guatemala and into Mexico. That first group, whose numbers have since diminished to approximately 4,000, reached the Oaxacan city of Juchitán this week, as a second, smaller caravan crossed into Mexico about 250 miles behind.

While Mexican authorities were ultimately able to impose order on what was initially a chaotic and aggressive entry by members of the first caravan nearly 12 days ago, migrants from the second group reportedly threw rocks and used sticks in a more violent confrontation with Mexican police, as they crossed the Suchiate River from Guatemala this week.

“They’re throwing rocks viciously and violently,” Trump said, declaring, “This isn’t an innocent group of people, large number of people who are tough.”

Although he insisted “there’s nothing political” about his policy, Trump appeared to be talking directly to voters as he warned that the “Democratic Party’s vision is to offer [these migrants] free welfare, free health care, and even the right to vote.”

“Hard-working taxpayers will be asked to pick up the tab,” he said.

According to the Washington Post, Trump had initially planned to unveil a new immigration policy Tuesday, but postponed the announcement in the wake of the Pittsburgh synagogue massacre.

On Twitter Wednesday, Trump repeated unsubstantiated claims about those traveling in the migrant caravans coming from Honduras and El Salvador.

“We will NOT let these Caravans which are made up of some very bad thugs and gang members, into the U.S.,” he tweeted. “Our Border is sacred, must come legally. TURN AROUND.”

In fact, in order to seek asylum in the United States, an individual must first be physically present in the country. Under current law, migrants can legally pursue asylum at the border either by presenting themselves to border officials at one of the 48 official ports of entry between San Diego and Brownsville, Texas, or else by turning themselves in once they cross the border.  Experts have warned that efforts to block these legal paths to entry, which are now used by the majority of Central American migrants, will not reduce the number of asylum seekers but will drive more of them to pay for the services of smugglers and put themselves in danger to cross the border without getting caught.