President Donald Trump is about to get nearly $4 billion to build his much-desired wall on the southern border with Mexico — but it will come at the expense of the US military.

Pentagon officials on Tuesday said that the Defense Department will take out $3.6 billion from 127 existing military construction projects and reallocate those funds to put up about 175 miles of wall. Half the money will come from projects originally meant for the US and its territories, and the other half from international ones.

The administration had announced last February it would make such a move, so it’s not entirely unexpected. But it’s still unclear which specific military projects will be delayed by this decision, as the Pentagon said it didn’t want to release that information before notifying members of Congress on Wednesday.

That’s an important political matter. Military construction projects mean jobs and funding for certain districts, many of which rely on that money to sustain their economies. Politicians representing those districts and states will probably not be too happy to learn that their constituents are among those who might be affected.

Senate Minority Leader Chuck Schumer is already irate because he says West Point — the Army academy located in New York state — is slated to lose funds.

“This decision will harm already planned, important projects intended to support our service members at military installations in New York, across the United States, and around the world,” Schumer tweeted Tuesday evening. “It is a slap in the face to the members of the Armed Forces who serve our country that President Trump is willing to cannibalize already allocated military funding to boost his own ego and for a wall he promised Mexico would pay to build.”

What the reallocated money will help build

Deputy Undersecretary of Defense Elaine McCusker told reporters on Tuesday that the money will go toward building new parts of the wall and replacing certain existing sections. The first focus will be on 11 areas in California, Texas, and Arizona. Construction could begin as soon as three months from now on land owned by the Defense Department, with others on public land to come down the line.

McCusker also nodded to the fact that some military projects will be halted for the time being because of this move. “We do realize this could cause some delay,” she told reporters, but “they are definitely not canceled.”

It’s unlikely that will mollify lawmakers who waited for months to hear what would lose out to the Trump’s desire to erect a wall.

“[H]e made it clear he is willing to take funds from our troops and disaster victims and divert them to try to protect his political right flank,” Sen. Jack Reed (D-RI), the top Democrat on the Senate Armed Services Committee, said in a Tuesday statement. “And ultimately, that could put Americans at risk.”

But it’s possible that building more of the wall might lead to the end of another thing Democrats despise: Trump’s deployment of US troops to the border.

Trump sent roughly 5,000 troops to the US-Mexico line last fall after declaring a national emergency, with the main purpose of supporting Border Patrol and other officials in doing their jobs. None of them have been authorized to engage with migrants in any way, but critics still say having thousands of active-duty troops there keeps them away from preparing for bigger things like a future war with China or Russia.

But if a lot of the wall goes up — and Trump is satisfied that fewer migrants can enter the US outside of approved checkpoints — then he may recall some troops to their garrisons.

“In areas where we go from, say, a vehicle barrier to a 30-foot wall, we will have a significantly new set of capabilities that didn’t exist previously,” Jonathan Hoffman, the chief Pentagon spokesperson, told reporters on Tuesday during a briefing.

Still, it does appear at least some portion of Trump’s wall will go up in the near future — and the military will pay for it one way or the other.