During his presidential campaign, no single promise electrified Donald Trump's supporters more than the pledge to build a "big, beautiful wall" all along the border with Mexico.
Wednesday, President Trump turned that promise into an executive order, one of two he signed. His directive leaves many questions unanswered about what sort of wall might be built, how much it would cost and how it would be paid for.
The two orders, however, do begin the crackdown on illegal immigration that Trump promised his supporters. In addition to the wall, he would greatly expand deportations and detention of migrants and block federal money for so-called sanctuary cities.
Some of the actions will be felt immediately, some require more cash from Congress, others will only take effect over time.
Here's a look at what the actions mean and what they don't.
Trump ordered the "immediate construction of a physical wall on the southern border" and gave the Homeland Security department six months to study how to prevent "all unlawful entries" into the U.S. — a goal that is widely considered impossible. But "immediate construction" doesn't mean a wall will be built all along the 2,000 miles of the Mexican border any time soon. Trump's order directs Homeland Security to come up with a long-term plan for getting it done.
Cost estimates for walling off the entire border run from $12 billion to $38 billion, and the barriers would cost billions more to maintain over time.
Trump could tap some existing federal funds to begin construction. U.S. Customs and Border Protection already has budgeted $175 million for "procurement, construction and improvements." That wouldn't be nearly enough to finish the job, but it would allow a start.
Trump has famously said Mexico would pay for the wall. Mexican officials say no. Asking Mexico to pay for the wall is "unacceptable," Mexico's foreign minister Luis Videgaray has said.
Trump aides have floated the idea of taxing cash that flows back to Mexico from workers in the U.S. or using the wall construction as leverage in negotiations to change the terms of the North American Free Trade Agreement.
Trump promised Wednesday to help Mexico by stopping the flow of illegal cash and guns moving south from the U.S. He is scheduled to meet with Mexican President Enrique Peña Nieto next week, but Peña Nieto is under pressure at home to cancel the meeting in the wake of Trump's announcement.
Currently, about 600 miles of the border have some form of fence, ranging from the imposing barrier along parts of the California border to more traditional fencing elsewhere. Building all that already cost about $7 billion. The government uses walls and fencing in highly trafficked urban areas where border agents have only minutes to apprehend illegal crossers. Cameras and sensors are used in more remote areas.
Border Patrol agents have long said that what they need to reduce illegal border crossings further is more of those cameras, sensors, vehicles and equipment and not more physical barriers. Smuggling cartels often use blow torches to cut holes through existing border walls or dig tunnels under them, they say.
The government has has also increased the size of the Border Patrol from about 10,000 agents in 2004 to 21,000 today. Trump plans to add an additional 5,000 agents.
The increase in security — plus economic changes in both the U.S. and Mexico — has meant fewer people are crossing back and forth over the border. The Pew Research Center estimates that in recent years, more Mexicans have been returning to Mexico than migrating to the U.S.
There has been a dramatic increase in Central American migrants arriving at the border in Texas, but a large share of those people are not trying to evade capture. Instead, they quickly surrender to border agents and make claims for asylum, saying they are fleeing the violence in their home countries.
Deporting more people
Under Trump's plans, immigration officials will have much more freedom to deport people they find in the country illegally. President Obama tried to focus the deportation force on removing people with criminal records and those who pose a threat to public safety, and deportations from the interior of the country declined during Obama's second term.
Trump dramatically expanded the list of people considered a priority for removal to include those charged with crimes, even if a trial has not yet been held, and those who have improperly received any welfare benefit. As a result, a lot more people will be unable to win reprieves from deportation even if they have strong family ties in the U.S.
Immigration officials can act on these new priorities immediately. There are about 800,000 people in the U.S. who already have a final order of removal from an immigration judge and have either refused to leave or been allowed to stay temporarily, often because of the hardship their deportation would cause to family in the U.S.
Also, countries that refuse to take back people being deported from the U.S. have been put on notice by the Trump administration that they must accept return of their citizens. About 23 countries currently don't accept deportations from the U.S., including Afghanistan, Algeria, China, Iran, Iraq, Libya, Somalia, and Zimbabwe.
Courts have ruled that people from such countries can't be held indefinitely, even if they have a violent criminal conviction. As a result, more than 8,000 immigrants with criminal records have been released in the past three years.
Trump also instructed immigration officials to expand the number and size of detention facilities to hold asylum seekers and people awaiting hearings in immigration court. Cases for people held in detention can move more quickly, and they can be deported faster than those released and told to appear in court.
Advocates for immigrants are concerned about the poor conditions in detention facilities, many of which are also local jails and have a track record of substandard medical care. Also, immigrants in detention facilities have a much harder time getting lawyers.
Major cities including Los Angeles, San Francisco and Chicago currently don't allow federal immigration officials access to their local jails to check the immigration status of inmates and will only notify deportation officers if a serious, violent offender is being released.
Trump ordered federal agencies to withhold federal grants from cities that "willfully refuse to comply" with immigration laws. How broadly the administration plans to interpret that language remained uncertain. White House officials could not say Wednesday exactly which categories of federal funds would be targeted.
The most likely pots of money to be affected would be those overseen by the departments of Justice and Homeland Security. That includes grants to local police for purchasing new equipment and for training, as well as reimbursement to local jails for holding prisoners and detainees for the FBI, the U.S. Marshals Service and immigration officials. For some counties, those funds are a sizable chunk of their law enforcement budget.
In addition, Homeland Security oversees millions of dollars in emergency management grants that state and local law enforcement, fire departments and EMT units use to buy new equipment and train workers.
But cutting off those funds will launch a legal fight with cities and states that could be mired in courts for years.
New York Atty. Gen. Eric T. Schneiderman said Wednesday he would "do everything in his power to fight" Trump's order to cut federal funds to so-called sanctuary cities. California Assembly Speaker Anthony Rendon (D-Paramount) said the state, which recently hired former Atty. Gen. Eric Holder to help fight the Trump administration, was "examining ways the state can aid sanctuary cities."
Trump also ordered an expansion of a program called 287(g) that trains local police to enforce immigration laws. That program was scaled back by the Obama administration because of concerns it was being used in racially discriminatory ways.
Wednesday's orders also aimed to reinstate the controversial Secure Communities program, canceled and replaced by a voluntary program under Obama. Under the program, when a person is booked into a local jail, the nearby immigration office is automatically notified if the person is in the country illegally. Immigration and Customs Enforcement currently receives the alerts, but doesn't respond in every case.