Not even America’s closest trading partners were spared by a policy broadside that spooked investors and left policymakers scrambling to formulate responses.

For decades, global commerce abided by tariff rates agreed to by the U.S. and 122 other countries during the 1980s and 1990s. On Wednesday, Trump detonated that arrangement, saying that other countries had exploited the system and “ripped off’’ the United States for years, causing its once-mighty manufacturing base to shrink.

The penalties announced on Wednesday unleashed turbulence across world markets and drew condemnation from other leaders facing the end of an era of trade liberalization that has shaped the global order for decades.