If the U.S. military were to strike North Korea for the reasons Graham mentioned, it would be the result of a calculation that sparking a real conflict in East Asia is preferable to accepting a theoretical threat to the United States—that it’s worth risking the actual deaths of those living in and near North Korea, including American expats and troops stationed in Japan and South Korea, to avert the potential deaths of Americans at home. When I surveyed experts this spring, they predicted that whatever form U.S. strikes against North Korea take, they could result in thousands or even millions of deaths—as the North Koreans retaliate with conventional, chemical, and perhaps nuclear weapons, and the United States and its allies respond in kind, dragging the region into a spiral of conflict. The vast range of the casualty estimates spoke to just how much unknown risk U.S. military planners would be assuming.

Graham is advocating “preventive strikes,” which differ from “preemptive strikes” in that they would not be a response to imminent attack by North Korea. He’s not suggesting that the U.S. military spring to action should it believe that Kim Jong Un is about to nuke California. He’s suggesting that the U.S. military neutralize the North Korean nuclear threat so Kim never has the ability to nuke California. As my colleague Peter Beinart has written, postwar American policymakers associated preventive war with Nazi Germany and Imperial Japan, and therefore tended to reject the approach on moral grounds. But since the end of the Cold War, preventive military action has become a popular option among U.S. officials, culminating with George W. Bush’s invasion of Iraq.

When members of the Trump administration publicly discuss military options against North Korea, they typically describe them in preventive terms. It’s not surprising that a hawk like Lindsey Graham would characterize the president’s views that way. But you don’t have to take his word for it. H.R. McMaster, the president’s national-security adviser, has staked out a similar position. In April, he said it would be unacceptable for the North Korean government to obtain nuclear weapons that can reach the United States, even if that entails taking military action that would produce “human catastrophe” in South Korea. In July, Joseph Dunford, the chairman of the Joint Chiefs of Staff, engaged in the same grim calculus.

“Many people have talked about military options [against North Korea] with words like ‘unimaginable,’” he observed. “I would shift that slightly and say it would be horrific. It would be a loss of life unlike any we have experienced in our lifetimes. Anyone who has been alive since World War II has never seen the loss of life that could occur if there’s a conflict on the Korean peninsula.” (Defense Secretary James Mattis has similarly described a potential second Korean war as representing “probably the worst kind of fighting in most people’s lifetimes. ... [T]he bottom line is it would be a catastrophic war.”)