Suppose Joe Biden wins reelection. Will he revise his approach to national security and foreign policy? He should, don't you think?
He capitulated to the Taliban in Afghanistan in just about the most damaging way imaginable. He failed to deter Vladimir Putin from launching a war against Ukraine. He has vowed to defend Taiwan from the Chinese Communists but isn't equipping the U.S. military for such a mission. He has enriched and empowered Iran's rulers whose nuclear weapons program is rapidly advancing while their proxies attack commercial shipping in the Red Sea and wage a multifront war against Israel. Shall I go on?
Now suppose Donald Trump returns to the White House. Though he is famously unpredictable, there may be a select few who have insights into his thinking.
For example, there's Robert O'Brien. He served as President Trump's national security advisor from 2019 to 2021. They apparently got on well.
Mr. O'Brien has a long article in the current issue of Foreign Affairs: "The Return of Peace Through Strength: Making the Case for Trump's Foreign Policy."
He predicts that a "second Trump term would see the return of realism with a Jacksonian flavor" – the reference is to Andrew not Jesse – and that "Washington's friends would be more secure and more self-reliant, and its foes would once again fear American power."
Peace through strength is not a new idea. It was given expression by the Roman emperor Hadrian, George Washington, and Ronald Reagan.
It implies that if a polity is strong enough, its enemies will be deterred. And should deterrence fail, those enemies will face defeat – a lesson for others.
A tough question follows: How much strength do you need to convince your enemies that it would be foolish for them to challenge you? The answer: More than you probably think.
If your enemies suspect they might be able to take you on, some are almost certain to try. And it is not sufficient that they know you have vastly superior power. They also must believe you have the political will to use your power effectively.
China is now ruled by the strongest Communist Party in history. Mr. O'Brien accurately observes that Xi Jinping is "China's most dangerous leader since the murderous Mao Zedong."
He notes that Mr. Xi "now has a committed and useful junior partner in Moscow," and that the Islamic Republic of Iran has joined both countries in "an emerging axis of anti-American autocracies."
One result is that Tehran has felt freer "to attack Israel, U.S. forces, and American partners through proxies and directly."
Meanwhile, Mr. O'Brien adds, the U.S. military has "resumed a gradual decline that began during the Obama administration before pausing during Trump's time in office."
Are you about to object that building the strength necessary to seriously deter Beijing and its partners would be too expensive? If so, let me remind you that deterrence, however costly, is cheaper than war.
Along these lines, Mr. O'Brien prioritizes the need for a larger U.S. Navy, "technical and numerical superiority to the combined Chinese and Russian nuclear stockpiles," and "massive investments" in hypersonic missiles, new weapons that "travel at more than five times the speed of sound and can maneuver within the earth's atmosphere." Because funding for such missiles was drastically reduced by President Obama, both China and Russia are far ahead on these game-changing missiles.
But Mr. O'Brien then adds that "large increases to defense expenditures are unlikely regardless of which party controls the White House and Congress. Spending smarter will have to substitute for spending more in a contemporary strategy of peace through strength."
I'm afraid that's a copout. If we are in a second cold war against a more challenging combination of adversaries than we faced in the first cold war, and if we want this struggle to come to a Reaganesque conclusion – "We win, they lose" – it will be necessary at least to return to the spending levels of the Reagan years, the years before the Soviet Union collapsed and the U.S. took a premature peace dividend and a holiday from history.
Smarter spending is a necessary but insufficient condition for building the strength required to achieve deterrence and preserve peace.
A president who grasps all this should be capable of making a persuasive case to the American people. He might ask: Do you prefer peace through strength or war through weakness? Because there's no third option.
Such a president also would adopt policies that strengthen America's economic power so that when the U.S. imposes sanctions, they bite hard.
Mr. O'Brien stresses that "American first is not America alone," and that a "successful foreign policy requires joining forces with friendly governments and people elsewhere." Those governments and people must contribute to the collective security.
There's lots more in Mr. O'Brien's article, including other arguments about which I'm skeptical. (For example, is it really a good idea to deploy "the entire Marine Corps to the Pacific"?)
Overall, however, Mr. O'Brien has outlined a coherent Trump Doctrine, based on what he calls Mr. Trump's "own instincts" and "traditional American principles."
He notes that "Trump has never aspired to promulgate a 'Trump Doctrine' for the benefit of the Washington foreign policy establishment."
Similarly, I'd point out, it was not President Reagan who first articulated the Reagan Doctrine. It was the late, great Charles Krauthammer who used that term in a 1985 Time magazine article to describe the Gipper's mix of foreign and national security policies.
Is Mr. O'Brien reading Mr. Trump correctly? Did Mr. Trump approve Mr. O'Brien's article before it was published? Will there be a second Trump administration?
These are just some of the questions that keep me up at night.