Quiz question: When and why did Britain annex Sudan? The answer is in 1899, after a decade and a half of fighting. British forces were up against Sudanese militias that had rallied under the banner of a charismatic Islamic leader who styled himself as the Mahdi, and whom the British viewed as a fanatical terrorist.

There is a history lesson worth learning here about imperial overreach, as the United States leaves Afghanistan. Many voices warn that what follows will be instability and eventually a Taliban takeover. The country will once again become a base for terrorism, they argue, and so we must stay to keep it stable and in friendly hands.

The truth is, since 9/11, Washington and most advanced governments have developed a powerful capacity to intercept terrorists, track them down and prevent them from launching large-scale attacks. Groups such as al-Qaeda and the Islamic State are in tatters, hunted everywhere and fragmented into local forces. They operate in various unstable countries, such as Afghanistan, Mali and Yemen. This is an argument for global counterterrorism efforts, not the sustained occupation of any one particular place.

But the mentality that drove the U.S. occupation of Afghanistan and Iraq was an imperial aversion to any instability. During the late 19th century, Britain worried that instability in Sudan — especially from Islamist terrorists — would spill over and threaten British access to the Suez Canal in Egypt. That canal provided the lifeline to the sea lanes to India, which was the jewel in the crown of the British Empire. As the globe’s superpower, Britain had similar fears in many parts of the world. So London sent tens of thousands of troops to fight wars in Sudan and elsewhere, annexing remote provinces in Africa and Asia (including some areas in Afghanistan!) — all of which turned into massive burdens for Britain. The British allowed the tail to wag the dog.

The parallel is not exact, of course, but the United States is the world’s sole superpower, for now. It would be unfortunate if the Taliban retook Afghanistan, and Washington should support the Kabul government and work with other countries in the region — China, India, and above all, Pakistan — to find a sustainable power-sharing arrangement in Afghanistan. But Washington must also keep in mind, as the Biden administration appears to be doing, that U.S. forces have spent two decades in Afghanistan. They have done what could be done, successfully degrading al-Qaeda and killing Osama bin Laden. Ultimately, Afghanistan is not central to the United States’ position as a global power.

Britain’s greatest mistake during its imperial expeditions at the turn of the 20th century was its failure to distinguish between its vital interests and those that were peripheral. By contrast, the most brilliant American strategist of the Cold War, George F. Kennan, always said the Cold War depended on a small number of power centers. He argued in the late 1940s that there were just five — the United States, Britain, the West German region, Japan and the Soviet Union. As long as Washington could maintain the 4-to-1 ratio against Moscow, it would win the Cold War.

Kennan urged a steely-eyed focus on these centers of power. “We must decide which areas are key areas, and which ones are not, which ones we must hold with all our strength and which we may yield tactically,” he said. Instead, Washington came to intervene in far-flung places all over the world to prevent communists from gaining power anywhere. This was a fool’s errand, and it produced only self-inflicted wounds. Strategy must be based on interests, not a reflexive response to any and all threats.

Henry Kissinger, a realist like Kennan, had been a skeptic of the Vietnam War as an academic. As a member of the Nixon administration, he supported vigorously prosecuting the war while negotiating the withdrawal of American troops. But in his private conversations with Richard Nixon, he revealed that he did not believe in the central logic that had guided American intervention. It didn’t really matter if South Vietnam fell, he told Nixon, and as long as it happened “a year or two” after U.S. troops were gone, the American public wouldn’t “give a damn.” South Vietnam did fall, and it caused a humanitarian tragedy, but in the long run it did not cripple the United States. Only a few minor dominoes fell to communism in Asia, and 10 years after the fall of Saigon, the Reagan administration was negotiating from a position of strength with the Soviet Union. By 1989, the Berlin Wall fell.

A key reason for the collapse of Moscow’s empire, of course, was its intervention in Afghanistan, which bled the Soviet Union and sapped its will. The Russians got involved for familiar reasons: an insurgency, internal divisions, a fear of instability. Moscow should have paid attention to George Kennan’s sage advice then, as we should now.

clarification

An earlier version of this article was unclear in describing that portions of Afghanistan were ceded to Britain after the Second Anglo-Afghan War ended in 1880. This version has been updated.

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