Donald Trump is enacting a severe immigration crackdown. Here's what you need to know.

Donald Trump signaled on Tuesday night that he would move ahead with his plans to build a massive wall on the border with Mexico, as well as institute severe restrictions on Muslim immigration into the United States—two key controversial promises from his presidential campaign.

Trump touted the plans in—what else?—a tweet.

Here’s what you need to know.

Trump is targeting Muslims.

Reuters, citing unnamed congressional sources, reported late Tuesday night that Trump will sign a series of executive orders to block visas for people attempting to enter the U.S. from Syria, Libya, Iraq, Iran, Somalia, Sudan, and Yemen. While couched in geographic terms, the implication is clear—this is a Muslim ban in everything but name. Trump is also expected to “temporarily restrict access to the United States for most refugees,” Reuters wrote, until a system for what Trump refers to as “extreme vetting” can be put into place.

In response to initial reports of the immigration ban, Nihad Awad, executive director of the Council on American-Islamic Relations, tweeted that the rulings will “not make our nation safer” but “more fearful and less welcoming” instead.

The wall is coming too.

In addition, Trump is expected to sign an order on Wednesday to begin construction on his much-touted wall along the United States’ Southern border. While he has long insisted that Mexico would, in fact, shoulder the financial burden of the wall’s creation, Trump in recent weeks has said he’d rather begin construction first, with Mexico to pay the money back later—a claim vehemently denied by Mexican President Enrique Peña Nieto, who, coincidentally, is scheduled to visit the United States at the end of the month.

As NPR pointed out, Trump may very well have the authority to begin construction on the wall, thanks to Secure Fence Act of 2006, which included a provision on building a a two-layered fencing system along the border.

Nevertheless, outgoing Customs and Border Protection agency commissioner Gil Kerlikowske seemed to pour cold water on the necessity of Trump’s cornerstone initiative, telling ABC News in an interview earlier this week that he didn’t think the wall was “was feasible” or “the smartest way to use taxpayer money on infrastructure.”

Trump meant it.

Anyone who thought that Trump wouldn’t follow through with these campaign promises has been proven wrong. He was serious, and it’s happening.

UPDATE: He really, really meant it.

On Wednesday afternoon, Trump went to the Department of Homeland Security and signed two executive orders related to the border wall and broader immigration policy. (Actions related to refugees and immigration from the Middle East have not been signed yet.)

In an interview Wednesday with ABC News, Trump suggested that construction of the wall would begin in “months,” but admitted that taxpayer dollars would be necessary to start the project.

“We’ll be reimbursed at a later date from whatever transaction we make from Mexico,” he told ABC’s David Muir. “I’m just telling you there will be a payment. It will be in a form, perhaps a complicated form. What I’m doing is good for the United States. It’s also going to be good for Mexico. We want to have a very stable, very solid Mexico.”

Trump’s press secretary Sean Spicer added more details in his daily briefing. One executive order will direct funding to the wall and increase the detention space used to jail undocumented immigrants. Another will look at ways to strip so-called “sanctuary cities” of federal money, and restore the controversial “Secure Communities” program, among other things.