Fear, the new book by journalist Bob Woodward about the Trump administration, describes how U.S. officials consider the use of cyberattacks and weigh them with other types of military action.

The book, which was officially released Sept. 11, highlights how both the Obama and Trump administrations used cyberattacks as a response to activity in another domains. It also sheds light on how the United States relies on cyberspace to deter actions.

Woodward describes how the Obama administration used cyberattacks as one method to deter a North Korean nuclear launch. From the onset of the Obama administration, the book describes how U.S. intelligence officials targeted the “command, control, telemetry and guidance systems, before or during a North Korean missile test launch.” In 2017, the New York Times reported Obama ordered the Department of Defense to ratchet up their cyber and electronic strikes against North Korea as a way to sabotage the country’s missile program.

But as the Obama White House considered more cyberattacks on North Korea, Fear describes how U.S. officials were wary of the second-order effects. North Korea’s internet servers traveled through China, where leaders might believe they were being attacked. Such an event could unleash “a cataclysmic cyber war,” Fear notes. One senior Obama cabinet member warned the president that “I can’t promise you that we can absorb a cyber counterattack.”

As the Trump administration forged its own plan to pressure North Korea, Woodward reports that the Defense Department used cyber-activity to “demonstrate capability and show the threat” of U.S. forces. But it is clear that the cyber campaign was used in concert with other tools to deter North Korea, and were tightly calibrated. “These actions were not to trigger a limited conflict,” Woodward writes.

But perhaps the vignette in the book most likely to spark discussion in the cyber community was a meeting between Trump and his former Homeland Security adviser, Tom Bossert. Before Bossert was due to appear on TV in the spring of 2018, he wanted to run his talking points by the president.

“You and your cyber,” Trump said, according to Woodward’s account, “are going to get me in a war — with all your cyber shit.”

Bossert responded by saying that “I’m trying to use other elements of national power to prevent bad behavior online,” and explaining how he needed to coordinate cyber policy with the economic policy. “That’s the point, sir.”