From the very start of his campaign for the U.S. presidency, Donald Trump has passionately promoted construction of a border wall between the U.S. and Mexico. He remains determined to get something built, even if it’s not as vast as he once envisaged, or made of concrete as he used to describe it, or financed by Mexico as he famously promised his supporters. Ever since Mexico refused to foot the bill, the wall’s funding has been ensnared in budget negotiations with the U.S. Congress that forced a record 35-day partial government shutdown and led to Trump’s declaration of a national emergency to secure more money for the wall.

1. Why a wall?

Trump, in his many public statements on immigration and border security, has said an “impenetrable” wall would “stop dangerous drugs and criminals from pouring into our country.” Trump and his aides also have talked up the notion that a wall might stop terrorists from entering the U.S. and curtail human trafficking.

2. How much wall already exists?

Barriers that mostly predate Trump’s presidency, ranging from 18-foot-tall iron fencing to makeshift vehicle barriers and barbed wire, span 654 miles of the almost-2,000-mile U.S.-Mexico border, mostly in California, Arizona and New Mexico. Most of the border land without any wall is in Texas along the Rio Grande River, and much of that is privately owned, meaning the federal government would need to purchase or seize it to build barriers. Land along the border cuts through cities as well as rural farmland, desert, arroyos, craggy mountains and wildlife reserves.

Existing barriers along the U.S. southwest border:

3. What exactly does Trump want?

In his presidential campaign, Trump called for about 1,000 miles (1,609 kilometers) of concrete wall, with natural barriers covering much of the rest of the border. At the Republican Party’s 2016 national convention, at which he became the nominee, the party adopted a platform stating “the border wall must cover the entirety of the southern border.” A Trump administration proposal early in 2018 called for a more modest 722-mile mix of wall and fencing, mostly updating what’s been in place for decades, while relying on drones and other methods to secure the rest. More recently Trump said he wants 500 to 600 miles of new wall, where needed, and built from steel rather than concrete.

4. How much more wall has Trump gotten built?

A May 22 report from U.S. Customs and Border Protection said work has been completed on 20 miles of wall, though it didn’t specify if any of that was renovation of existing fencing. Work has started on at least 32 miles of new fencing in Texas, and Congress approved funding for about 85 miles more. In addition, some existing fence is being renovated or replaced. The Defense Department, for instance, is building 131 miles of new barriers in place of dilapidated or outdated designs, according to Customs and Border Protection. Fact-checkers point out that this doesn’t fully support Trump’s assertions on Twitter and in other public comments that “we have already built large new sections” of wall. (Trump insists that renovations should count as new wall because it involves “complete demolition and rebuilding of old and worthless barriers.”)

5. How much would a wall cost?

Trump’s fellow Republicans in Congress have said they expect a wall to cost $12 billion to $15 billion, based on the cost to rebuild existing border fencing covering a third of that distance, though those projections don’t include the cost of buying non-government land. (The Trump administration could seek to use eminent domain to seize land needed for a border barrier as well as support roads and other infrastructure, though it would likely face legal challenges that could delay construction for years.) A July 2018 report by the U.S. Government Accountability Office warned that the wall might “cost more than projected, take longer than planned or not fully perform as expected.”

6. How much money has Congress pledged?

Almost $1.7 billion in 2017 and 2018, which includes the $641 million for new fencing in Texas, plus $445 million for replacement of existing primary pedestrian fencing along the border, $251 million for 14 miles of replacements for barriers in San Diego, and money for enforcement. As part of negotiations over fiscal 2019 spending, Trump asked for $5.7 billion, and Congress approved $1.375 billion, which is being supplemented by $601 million in Treasury forfeiture funds, which are raised by auctioning assets seized in criminal investigations.

7. What happened to Mexico paying for the wall?

Under former President Enrique Pena Nieto and current President Andres Manuel Lopez Obrado, Mexico emphatically refused to fund it. Trump has suggested that the U.S. can recoup wall expenses from Mexico via alternative methods, including by cutting its trade surplus with the U.S. through a renegotiated North American Free Trade Agreement. For a time he floated the idea of assessing a tax on the money that immigrants living in the U.S. send to their relatives in Mexico. Mexicans sent $28.7 billion in these so-called remittances in 2017, according to Banco de Mexico.

8. What do Democrats propose?

Generally speaking, Democrats say a better way to stop criminals and drugs from crossing into the U.S. would be to increase the number of border agents, improve technological surveillance, beef up security at ports of entry, and build barriers only where most needed. A wall like Trump proposes would be “immoral, ineffective and expensive,” House Speaker Nancy Pelosi, a Democrat, has said.

9. Would a wall stop drugs or migrants?

Some experts doubt that a physical wall would do much to reduce illegal drugs pouring into the country because they come mostly through established ports of entry. As part of a set of tools to combat illegal immigration, however, physical barriers could help. Israeli Prime Minister Benjamin Netanyahu praised Trump’s plan, saying a fence built along Israel’s border with Egypt has been a “great success” in keeping out migrants, mainly from African nations.

10. How about criminals or terrorists?

The Trump administration has said the wall is needed because the number of people on terror watch lists encountered at the southern border has increased during the past two years. Skeptics point to a State Department report issued in September 2018 that says there’s no credible evidence of international terrorists using Mexico as a base to send operatives into the U.S. The report said that while the southern border remains vulnerable to potential terrorist transit, “terrorist groups likely seek other means of trying to enter the United States.”

–With assistance from Erik Wasson, Jack Fitzpatrick and Michaela Ross.

To contact the reporter on this story: Mark Niquette in Columbus at [email protected]

To contact the editors responsible for this story: Sara Forden at [email protected], Laurence Arnold

©2019 Bloomberg L.P.