Iran has been escalating its actions against the United States and its allies, while President Donald Trump has been restrained, top administration officials said on Friday after the US air strike that killed Iran's top general raised fears that the two sides could plunge into a war.

And beyond the immediate tactical reason for the strike - ostensibly to stop major attacks across the region on Americans - the attack changes the game and sends a message that President Trump, while not wanting to get into wars overseas, is willing to use force.