BERLIN — Some framed it as another empty threat from a leader whose bark is consistently worse than his bite. Some saw a method to the perceived madness — a potentially shrewd act of brinkmanship.

And others considered it simply the latest act of an America that, long before President Trump, has often oscillated from isolation to intervention, and back.

Mr. Trump’s order to attack Iran on Thursday in retaliation for its downing of a spy drone, and his abrupt reversal minutes before American forces carried it out, have intensified global doubts about the president’s judgment and the power wielded by the United States.

The appearance of erratic decision-making “adds to the confusion of his allies and adversaries,” said Nigel Sheinwald, a former British ambassador to Washington who once conducted hostage negotiations with the Iranian government.