Since 2018, tariff policy has returned to the center stage of global affairs, catalyzed by U.S. efforts to rebalance trade relationships under Presidents Donald Trump and Joe Biden. As governments rethink the rules of globalization, reporters who previously had not been trade experts are being asked to cover this highly specialized area of business journalism. Those covering trade must understand not only how tariffs work, but also how they ripple across economies.

For most of human history, governments have taxed goods crossing their borders. Tariffs have financed empires, protected domestic industries, and punished foreign rivals. They’ve sparked wars, crashed economies, and redefined alliances. Yet the tariff war between the U.S. and China doesn’t fit neatly into any of the old molds. Rather than being a tool to nurture domestic industry or fill government coffers, tariffs are now being wielded as weapons in a sprawling contest over