U.S. and Allies Plan Fight From Afar Against Al Qaeda Once Troops Exit Afghanistan

Daunting challenges face the American-backed Afghan security forces. Over the past year, they have lost territory from repeated assaults by the Taliban and have relied on U.S. air power to push back the insurgents.

With the Afghan government’s credibility waning, militias — once the main power holders during the days of the Afghan civil war in the 1990s — have rearmed and reappeared, even challenging Afghan security forces in some areas.

“If the president authorizes it, we will still be able to provide some level of military support to the Afghan national security forces after we depart the country,” William H. McRaven, the retired Navy admiral who directed the raid that killed Osama bin Laden, said in an interview on Wednesday.

For the Pentagon and the intelligence agencies, a key issue now is how readily counterterrorism operations can be carried out from beyond Afghanistan. The history of such operations has a decidedly mixed record. Cruise missile strikes launched from distant ships against terrorist targets in Afghanistan have had a low rate of success.

The United States maintains a string of air bases in the Persian Gulf region, as well as in Jordan, and the Pentagon operates a major regional air headquarters in Qatar. But the farther that Special Operations forces have to travel to strike a target, the more likely the operations are to fail, either by missing their mark or resulting in a catastrophic failure that could kill American service members or civilians on the ground, according to officials who have studied the record.

Defense Secretary Lloyd J. Austin III, meeting with allies of the North Atlantic Treaty Organization in Brussels on Wednesday, cited the military’s ability to strike terrorist targets in far-flung hot spots “in Africa and other places” where few, if any, troops are stationed, apparently referring to drone strikes and commando raids in Somalia, Yemen and Libya in recent years.

“There’s probably not a space on the globe that the United States and its allies can’t reach,” Mr. Austin told reporters.