This issue of Jacobin takes a hard look at the politics of borders, examining their role in dividing the working class, enforcing economic and geopolitical hierarchies, and sustaining global inequality. Are borders a necessary defense against capital’s race to the bottom, or are they just another tool for splitting the working class and suppressing wages? What would a solidaristic immigration policy look like today, and what would a genuinely internationalist socialism consist of in a world still crisscrossed by national frontiers?