Against that hysteria, a few facts are in order. First, the caravan is hardly an anarchic and lawless endeavor. It is a group of desperate people fleeing, in accordance with internationally accepted rules, the very real horrors of the “northern triangle” of Honduras, Guatemala and El Salvador, one of the most violent regions in the world.

Under international treaties and its own laws, the United States is obliged to allow foreigners inside the country or at its ports of entry to apply for asylum. It’s a daunting process, beginning with a “credible fear” interview to determine if there’s evidence that the applicant faces persecution or death back home. If the applicant passes that, the next step is plunging into an immigration court system that can take years to reach a decision. More than three-quarters of asylum-seekers from the northern triangle who came before the court were rejected from 2011 to 2017, according to TRAC, a research institute at Syracuse University.

Those in the caravans know this, since they are generally accompanied on their trek by organizers who lay out their options. This spring, about 700 people left the Mexican town of Tapachula, on the Guatemalan border, on March 25. Their ranks eventually swelled to about 1,200, from infants to the elderly. Most chose to remain in Mexico, which, despite a flawed asylum program, has become a favored destination for migrants. About 300 continued to Tijuana. Organizers and lawyers told about 200, mostly children, that they had a chance to gain asylum after applying at the San Ysidro crossing into San Diego.

Organizations that monitor immigration say American officials have come up with a variety of tactics to discourage asylum-seekers. One is to separate family members; another, attempted with the current caravan, is to claim that the port of entry has “reached capacity.” (Attorney General Jeff Sessions began to address that on Wednesday by sending more Justice Department lawyers and judges to process cases at the border.)

Finally, 24 hours after they arrived, the first group of eight migrants — three mothers with four children and an 18-year-old man — were allowed to apply for asylum on Monday evening. There was no telling how many would be allowed to follow.