Seeing Trump’s tweets during the Yates hearings, Nichols unleashed a series of his own that said Trump’s raw and sometimes angry responses provide “golden” intelligence on how Trump thinks and acts to hostile foreign powers. Such countries normally spend heavily on intelligence to understand and anticipate the next moves of the president of the United States.

“It shows how the president reacts under stress,” Nichols tweeted. “It’s something you never want the enemy to know. And yet it’s all out there, every day.”

In an interview, Nichols stressed that he was responding as an individual and not on behalf of the Naval War College, Harvard, Georgetown or any other institution where he lectures. He is the author of a new book, “The Death of Expertise,” and has previously written on the Russian presidency, the Cold War and future wars. He was a five-time, undefeated champion on the game show “Jeopardy.”

Now, Nichols worries that Trump’s tweets put Americans in jeopardy in ways they are not considering.

Nichols, who worked for the late Sen. John Heinz, R-Pa., had previously leveled criticism at Trump’s predecessor, Barack Obama, for too often laying out his thoughts and emotions before the cameras, giving too much to potential adversaries.