Donald Trump’s administration is laying the groundwork to build a wall.

Mexico might, ultimately, foot part of the bill for it. It might not. But within months of Trump taking the oath of office, his administration will (if everything goes according to plan) have money from Congress to build the wall (or at least some sort of “physical barrier”) across hundreds of miles of the US-Mexico border.

The plan to ask for money from Congress first, and Mexico later, appears to violate one of Trump’s core campaign pledges. This is a man who spent months on the trail engaging rallies in a call and response: “Who’s gonna pay for it?” “MEXICO!”

But this could be the best strategy for Trump and his team to, in fact, get some sort of wall built — one rooted in the Trump team’s belief that it has the upper hand right now, against both Congress and Mexico.

Building a wall would represent an enormous change in the American attitude toward immigration, toward Mexico, toward its welcoming image in the rest of the world. It would have massive (and probably unanticipated) effects on immigration into and emigration out of the US, and it would very probably cost human lives. That’s true no matter who pays for it.

That’s the promise Trump made when he promised to build the wall. Here’s how he’s planning to keep it.

Trump’s team wants to get the wall built quickly — and force Congress to get on board

Initially, according to reports from Politico’s Rachael Bade and John Bresnahan and the Washington Post’s Robert Costa, the administration plans to have the United States pay for the wall. The Trump transition team and House Republicans have a plan to include funding for a “physical barrier” in a spring appropriations bill, using a 2006 law that allowed the government to build barriers across 700 miles of the US/Mexico border. (The government has built some sort of barrier across most of those 700 miles in the ensuing decade, but only a few of them have the “double fencing” that Republicans say they originally wanted built.)

Trump himself, in a tweet Friday, emphasized that the administration could still ask Mexico to reimburse the US for the costs of the wall (something his campaign also said before the election) and emphasized that going the congressional route made sense “for speed”:

The dishonest media does not report that any money spent on building the Great Wall (for sake of speed), will be paid back by Mexico later! — Donald J. Trump (@realDonaldTrump) January 6, 2017

In this case, he’s correct. Trump’s team (and House conservatives) is trying to make sure that the government starts to move on a wall within the first few months of the Trump administration. And it wants to make sure Congress is committing, on the record, to the wall.

By putting wall funding in an appropriations bill, the House GOP hopes to force Democrats to choose between voting for the wall and shutting down the government. The Trump administration-in-waiting, meanwhile, is looking at it as a way to “break” the few remaining members of the party who are still wary of Trump’s immigration hawkery:

As several told me, Trump and top aides want Rs in Congress to "buy in." They see wall as way of breaking GOP's immigration moderates. — Robert Costa (@costareports) January 6, 2017

If anything, the plan to get congressional money for some sort of “wall” appears doable because Trump insiders have more reason to believe they can work out a deal with Mexico to pay for it.

Mexico is in really rough shape right now. The country is facing nationwide protests (and occasional outbreaks of violence) because gas prices are rising and the peso is falling — and the peso is falling because of speculation about what’s going to happen under a Trump administration.

Mexico’s government understands that it needs good relations with the US. President Enrique Peña Nieto just brought back Luis Videgaray, the former finance minister who arranged for Trump to visit Mexico during the campaign (and all but got sacked for it), to serve as foreign minister.

Trump’s administration-in-waiting thinks it can work with Videgaray, according to Costa. They know they have the upper hand. Mexico knows that too. And both sides know that moving to build a wall will put huge pressure on Mexico. Because they know that who pays for the wall is ultimately less important, and has less of an impact, than the fact that a wall exists.

Building a wall would be a huge deal, no matter who paid for it

Again, it’s still not entirely clear that the “wall” Congress plans to appropriate money for this spring will actually be a brick-and-mortar (or marble-and-gold) wall. It might be a double-sided fence that gets called a “wall.” It might be something flimsier still.

But it sure seems something along those lines is going to become reality.

This wasn’t readily apparent before this week. Even many Trump supporters (like Peter Thiel) and immigration hawks like the Federation for American Immigration Reform’s Dan Stein have implied that “we’re going to build a wall” was just rhetoric; Thiel called it a “metaphor” for enforcing existing immigration laws.

The incoming administration, though, is not proposing to build a metaphor. It’s proposing a physical barrier. And physical barriers have massive policy consequences. The buildup of border security in the late 1990s and 2000s led millions of unauthorized immigrants to settle in the US; hundreds of people have died trying to avoid fenced-off regions of the border by crossing inhospitable desert instead.

The implications of the wall — demographic, environmental, symbolic — are huge. That’s why Mexico is so worried about it. It’s why Thiel and other Trump defenders dismissed it as an exaggeration to avoid having to answer for the consequences.

All of this is true no matter who pays for the wall. It’s true, to a certain extent, even if the wall is simply a fence.

The Trump administration wants to make sure this happens. It’s making it much more likely. Even if Mexico doesn’t pay for it, there is, almost certainly, going to be something called a wall.