WASHINGTON — By inflicting tariffs on the steel and aluminum of his allies, and then on tens of billions of dollars in goods from China, US President Donald Trump has quickly moved to fulfill the tough campaign pledges he made on trade.

During his first year in office, Trump and his top economic aides made repeated threats and warned that preliminary investigations were launched into whether certain imports were being unjustly subsidized. But no concrete steps were taken. That all changed in March, when the "America First" president went on the offensive.