After Michael Waltz, the national security adviser, inadvertently included The Atlantic ’s editor in chief in a group chat about military attack plans on the Signal messaging app, he found himself on very thin ice with his boss.

U.S. President Donald Trump's national security adviser Mike Waltz is being forced out of his job, four people briefed on the matter said on Thursday, in the first major shakeup of Trump's inner circle since he took office in January.