A child traveling with migrants from Central America waits to enter the U.S. border and customs facility on April 29. (Jorge Duenes/Reuters)

ATTORNEY GENERAL Jeff Sessions is indifferent about whether undocumented immigrants crossing into the United States are simply seeking a better life for themselves and their families or whether they are fleeing domestic abuse, drug cartels, extortion rackets or political violence. It’s all the same to Mr. Sessions, who said Monday that all those who come into the country illegally would be prosecuted — and separated from their children in the bargain. Thus has the top law enforcement official in the United States enshrined callousness as administration policy.

Will babies be separated from nursing mothers? Will toddlers be housed in institutions far from parents? How many children will be traumatized by being carted away from their parents for weeks or months — or longer? The attorney general doesn’t say or, apparently, care.

Mr. Sessions’s policy of separating parents and children is intentionally and unapologetically punitive. There was no talk from him of developing additional detention centers that could accommodate families while parents await prosecution for the misdemeanor of illegal entry. There was no public recognition of the United States’ historical role as a beacon for refugees, nor its obligation in law and international treaty to accept migrants seeking asylum from danger in their native countries. There were no estimates of how many children will be removed from their parents, for how long, and with what long-term damage to their emotional and psychological welfare.

Instead, the attorney general offered indifference. Proclaiming a new policy of “zero tolerance,” he rebranded the United States as a crueler place than the countries from which people are fleeing. And never mind that, in many cases, parents are seeking refuge in this country in order to escape violence and persecution — and to protect their children.

The impetus for the new stance, of course, is President Trump, who has made clear that his crusade against all immigrants, with or without documents, knows no limits. Having washed his hands of the “dreamers,” mainly teenagers and 20-somethings raised and educated in this country after being brought here by their parents, Mr. Trump need not travel a great moral distance to upend the lives of brand-new migrant families by removing children from their parents.

The administration’s stated justification is a surge in migrants in recent months. The number of apprehensions of those coming into the country without papers, especially from Central America, has spiked from a year ago. However, the overall flow of migrants over the southwest border is near a four-decade low.

In other words, Mr. Sessions’s talk of a “massive influx” of undocumented immigrants is a falsehood. Against his incendiary vow that the administration will not allow the United States to be “invaded” and “stampeded ” is the plain truth that the southwest border is more secure, and less frequently breached, than at any time since the Nixon administration.

Yet Mr. Trump and Mr. Sessions propose a breathtaking innovation: wrenching every small child away, as a matter of policy, from his or her family. They have now matched their demagoguery on immigration with malice.