Migrants trek in camouflage through dry desert terrain. Dune buggies roar up to the United States-Mexico border barrier.

ONE thing is hard to miss these days on the Mexican side of the border with the United States: the migrants are gone.

Dune buggies roar up to the United States-Mexico border barrier ... built huge WhatsApp groups to coordinate the first major migrant caravans traveling from Central America to the U.S., according ...