The other post-9/11 change in strategy was to pursue the terrorists overseas, to keep them on defense so they found it harder to attack us at home. This has largely succeeded. Afghanistan ceased being a jihadist sanctuary, and the U.S. attacked enclaves in Somalia, Yemen, Syria, Iraq and the Philippines.

Contrary to progressive myth, the U.S. has typically done this with the cooperation of local allies. Kenya has helped against al Shabaab in Somalia, and the Kurds in Syria and Iraq. The security disaster of Afghanistan is that we will no longer have a local ally to help with intelligence.

Yes, we know: The interventions in Iraq and Afghanistan were done at tremendous cost and with a strategy that arguably overreached. The debates over invading Iraq and nation-building will rage on. But the invasion of Afghanistan had to be done to pursue al Qaeda, and the mistakes were made later, though again we don’t recall good alternatives being offered over the last 20 years. Mr. Biden’s alternative of willy-nilly withdrawal has demonstrably been worse.