Defense Secretary Mark Esper explicitly said Sunday that he had seen no hard evidence that four American embassies had been under possible threat when President Donald Trump authorized the targeting of Iran’s top commander, raising questions about the scale of the threat described by Trump last week.

In a defining week for President Donald Trump on the world stage, national security adviser Robert O’Brien was a constant presence at the president’s side as the U.S. edged to the brink of war with Iran and back again....

The contrasts with O’Brien’s predecessor along the way — in secret consultations at Trump’s Mar-a-Lago resort in Florida, in the Oval Office...