President Donald Trump is taking a blowtorch to the rules that have governed world trade for decades. The “reciprocal’’ tariffs that he announced Thursday are likely to create chaos for global businesses and conflict with America’s allies and adversaries alike.

Trump spoke to reporters from the Oval Office about his decision, saying it was an “amazing day.” When asked if prices would rise as a result of the tariffs, he said that they “could go up somewhat” at first, but then “prices will also go down.”