The number of border crossers arriving in the United States via its southern border has soared in recent months, with 132,887 people detained in May. Many of those arriving are coming from Central America.

This migration has intensified because of violence, food insecurity, and a lack of economic opportunity. Many are fleeing countries with sky-high murder rates, including Guatemala, Honduras, and El Salvador. And years of drought are affecting farmers across the region. Entire crops have been lost in Guatemala, where more than half the population lives below the poverty line.

To avoid U.S. tariffs, the Mexican government agreed in June to contain Central American migrants, many passing through the country on their way to the United States. Mexico promised to deploy 6,000 troops—from its newly created Guardia Nacional, or National Guard—to patrol the crossing points and strategic smuggling routes across the country.

The security force was first sent to the country’s southern border with Guatemala.