In Soldiers and Kings, Jason De León shows how heightened border enforcement reshapes migration into a longer and more dangerous process that strengthens the position of human smugglers. Mexico’s Programa Frontera Sur, modeled on the United States “Prevention Through Deterrence,” breaks up established routes and pushes people into remote areas. These shifts make migrants vulnerable to state agents and criminal groups that patrol the new corridors, and the harsher terrain turns guides into essential companions rather than optional helpers. A growing illicit economy takes shape around this need, and organized crime gains control by taxing guides and benefitting from the enforcement policies meant to stop movement. The result is a far more expensive and lethal journey that does little to address the root cause of migration, such as widespread poverty and gang violence, or catastrophes like the COVID-19 pandemic and hurricanes.

The book traces how these security measures stretch out transit across Mexico and expose people to repeated dangers. Freight trains once allowed a relatively quick trip, but Programa Frontera Sur makes that impossible. Migrants now move on foot through jungle paths and along isolated highways to avoid checkpoints. The guide