For those of us present at the beginning of the war on terrorism, the effective surrender of Afghanistan to the Taliban just in time for the 20th anniversary of the 9/11 attacks has been a very jagged pill.

A younger me saw the plane flying low toward the Pentagon and smelled that building burning while driving to the White House at dawn the next morning. I remember being handed the text of the ultimatum to Taliban leaders by then-national security adviser Condoleezza Rice for inclusion in the Sept. 20 address to a joint session of Congress. I was with President George W. Bush in the Cross Hall at the White House when he announced the commencement of hostilities in the Afghan war.

None of us working for the president in those moments would have imagined that a future American president would regard the hasty withdrawal of American troops ahead of advancing Taliban forces as a vindication of his foreign policy views and a victory for his administration.

But at least in my case, anger at this abdication is tempered by a recognition that — in the broadest outlines — President Biden is correct about the future of the war on terrorism. A counterterrorism mission is more sustainable than a counterinsurgency mission. America’s “over-the-horizon capability” will determine future success or failure.

This shift did not, however, originate with Biden. A transition in the theory of the war on terrorism actually began in the closing years of Bush’s presidency. In his determination to transfer roles to Afghan authorities, and in his negotiation of a Status of Forces Agreement in Iraq that set a date for the withdrawal of American combat forces, Bush was moving the United States toward a counterterrorism stance. Bush’s aggressive use of drones and Special Operations forces was adopted, expanded and systematized by President Barack Obama. What some have called the second war on terrorism — the silent war of precision strikes and midnight raids — actually started during Bush’s second term.

This, in its own way, is a forever war. It involves the preemption of threats with lethal force across national boundaries on a moment’s notice. It is easier to conduct this war when the United States has bases of operation closer to dangers. Striking over-the-horizon from Bagram air base is more effective than over-the-horizon from Doha, which is more effective than over-the-horizon from Omaha. And identifying risks still often depends on local intelligence assets. But both Republican and Democratic presidents have accepted the basic theory of attacking from a distance to remove emerging terrorist threats — an aggressive redefinition of war in its own right. Biden may be embracing an alternative to counterinsurgency operations, but he is not adopting an alternative to war.

There are practical and ethical questions about this method of warfare. On what basis are lethal decisions made, and who makes them? Is this a role we would want to concede to other global powers in the future? Does the precision targeting of death make warfare too routine and acceptable?

Whatever the objections, this is not an authority that American presidents will easily surrender. Our country’s assumption of this preemptive role is, in many ways, a function of technological change. There is the technology that allows nonstate actors to make low-cost asymmetrical attacks that have enormous human and economic consequences. There is the technology that allows the identification and surveillance of emerging threats. And there is the technology that allows for the incapacitation of those threats with limited civilian casualties. Under these circumstances, any president will be held politically responsible for allowing foreseeable attacks on American citizens.

In conducting this continuing, over-the-horizon war on terrorism, what is the most likely event that would draw the United States back into a war of invasion, occupation and counterinsurgency? We know the answer by remembering the white-hot emotions of 20 years ago. Imagine a biological attack on the United States by al-Qaeda operatives sheltered by Afghanistan. Or a radiological attack from terrorists supported by Iran. A successful attack by a terrorist enemy would most likely result in another American ground war against a state sponsor of terrorism.

And who is most likely to invite such a catastrophic outcome? It is those who say the threat of terrorism is really a myth — despite contrary evidence every morning in the president’s daily intelligence briefing. It is those who argue that the war on terrorism has been a failure — even though the United States has been largely free from two decades of escalating terrorist violence. It is those who would have us unlearn every lesson of the 9/11 attacks and adopt a pose of defiant vulnerability. The alternative to success in the forever war on terrorism is not peace; it is the prospect of warfare on a greater scale.

Conspiracy theories blaming George W. Bush for the Sept. 11, 2001, terrorist attacks have been debunked, yet millions of Americans still believe them. (Kate Woodsome, David Byler/The Washington Post)