In an escalation of his trade war, President Donald Trump moved to put tariffs on nations that levy taxes and fees that hurt U.S. businesses.

Military strategists know a battle can begin in one theater but quickly move into another. Similarly, what begins as a trade war can evolve into something bigger. It’s a truth worth remembering as the United States imposes substantially higher tariffs on our trading partners, who have the ability to respond in unanticipated ways.