The problem with this view of border enforcement, current and former officials say, is that it won’t work. The measures that could actually deter migration are less bruising and physically obvious, veering off instead into a world that is legal, technical and bureaucratic — and could take months or years to show results.

Central American parents and children are coming in record numbers because the U.S. asylum system is dysfunctional, immigration courts are crippled by an 860,000-case backlog and federal courts have blocked the government from keeping children in custody for longer than 20 days. Migrants know that the strain on the system means they are likely to be hastily released into the United States and could stay for years as they await court hearings.

Trump needs legislative and technical remedies to patch these “loopholes,” experts say, and there are clear legal and moral obstacles to the use of physical force for a migration wave consisting mostly of families and children.

“Despite all the things the administration has done — send the military, separate families, the ‘Remain in Mexico’ plan — the numbers are going up, not down,” said David Lapan, a former Trump administration official who worked under John F. Kelly when Kelly ran the Department of Homeland Security.