A unmanned U.S. drone flies over southern Afghanistan in 2010. (Kirsty Wigglesworth/ASSOCIATED PRESS)

AT A time when Islamic jihadism has become a major threat in at least half a dozen countries, it’s important to acknowledge that the group that has posed the greatest threat to Americans and the U.S. homeland — the original al-Qaeda affiliate in Pakistan — has been devastated. By all accounts, U.S. counterterrorism actions — above all drone strikes — have eliminated several generations of the organization’s leadership and pushed its survivors into far corners of Pakistan and Afghanistan, where they have scant chance to concoct operations like that of Sept. 11, 2001.

This success, veiled by the secrecy of the U.S. operations but nonetheless very real, must be part of any evaluation of the tragic deaths of two hostages, including American Warren Weinstein, in a Jan. 15 drone strike. President Obama rightly apologized for the failure to detect the hostages inside a structure targeted by a drone and promised a review.

One consideration in such a review could be whether drone strikes not targeted at specific individuals — known as “signature strikes” — are still justified in Pakistan. Since Mr. Obama tightened procedures for drone attacks in 2013, their numbers have decreased dramatically; outside monitors have counted only about two dozen in Pakistan in the past year, with civilian casualties in the single digits. Nevertheless, it was a signature strike that killed the two Western hostages, as well as four al-Qaeda militants. Such attacks do not require a finding that the targets pose an imminent threat to the United States, though they must still involve a judgment of “near certainty” that no civilians will be killed.

A second consideration is whether drone strikes must still be carried out by the CIA or should be transferred to the Pentagon’s Joint Special Operations Command. Mr. Obama has said turning over the operations to the military is desirable, and we agree: That would result in more transparency and oversight, and it would allow the CIA to focus on what should be its overriding mission of gathering intelligence, rather than conducting military operations. CIA control over drones in Pakistan, and the accompanying secrecy, has been seen as necessary to preserve cooperation with Pakistani authorities. Yet now that U.S. drone attacks have been widely publicized, and Pakistan has launched its own aggressive campaign against the jihadists on its territory, that may no longer be necessary.

What shouldn’t be up for review is whether drone attacks will continue to be a weapon in the U.S. counterterrorism arsenal. It’s true that the strikes have generated a backlash in public opinion, especially in the Muslim world. We have frequently expressed concern that the Obama administration has not accompanied targeted military action with more robust efforts to stabilize the countries where it takes place — a failing whose consequences can be seen in the collapse of Yemen’s government. There is a danger that U.S. drone strikes could be taken as a model for action by Russia, China or other powers against opponents who are not terrorists.

Nevertheless, there is little question that drones are the least costly means of eliminating militants whose first aim is to kill Americans. “If we were not engaged against the terrorists,” CIA Director John Brennan said recently, “I think we would be facing a horrendous, horrendous environment.” He’s right.