“Over-the-Horizon Operations” in Afghanistan

by , | Sep 8, 2021

Over-the-horizon operations. Photo courtesy Chalk 2 for the 163d Attack Wing

The United States’ withdrawal from Afghanistan has rightly dominated the world’s attention. The suicide bombing at Hamid Karzai International Airport on August 26th, resulting in the loss of 10 Marines, 2 Army Soldiers, 1 Navy Corpsman, and 170 Afghan civilians, will be inextricably associated with the mission to end the “forever war.” The brazen ISIS-K attack serves as a grim reminder that the global threat from terrorism persists.

Concerning the future of counterterrorism targeting, the Biden administration has routinely promoted the DoD’s over-the-horizon capability which “will allow us to keep our eyes firmly fixed on any direct threats to the United States in the region, and act quickly and decisively if needed.” Essentially, the concept is that the United States will monitor terrorist groups like Al Qaeda and ISIS-K without boots on the ground; develop actionable targets by means of sophisticated intelligence operations; and launch aerial strikes from regional locations. While a relatively simple idea CENTCOM Commander, General Kenneth “Frank” McKenzie, candidly  acknowledged, “it’s going to be extremely difficult to do it, but it’s not impossible.”

For those who wondered what an over-the-horizon operation would look like, the wait was brief. On August 27th, the DoD executed a strike against an ISIS-K planner and facilitator in Nangahar province using an unmanned aerial vehicle (UAV). On August 29th, the DoD launched another UAV strike against a vehicle containing multiple ISIS-K suicide bombers. Although the operations occurred while U.S. troops remained at the airport, the administration highlighted that they were demonstrative of the U.S.’ over-the-horizon capability. Previewing future strikes, President Biden announced that he ordered military commanders to develop operational plans to target ISIS-K assets, leadership, and facilities to be struck “in a moment of our choosing.” From a U.S. perspective, the era of over-the-horizon operations in Afghanistan has arrived.

While the long-term feasibility of over-the-horizon operations remains to be seen, a less discussed question concerns the jus ad bellum legal justification for conducting such strikes. As of this writing, the Biden administration and Taliban have signaled a desire to retain cooperative diplomatic relations.[1] In addition to seeking Taliban support for future evacuations, the administration may seek to diplomatically hold the Taliban to its Doha promise to “not allow any of its members or groups, including Al Qaeda, to use the soil of Afghanistan to threaten the security of the United States and its allies.” Further, On September 1st, General Mark Milley, Chairman of the Joint Chiefs of Staff, acknowledged that “it’s possible” that the US would work with the Taliban to target ISIS-K in the future. Thus, this fragile and fluid cooperative U.S.-Taliban relationship warrants a speculative legal gaze at future over-the-horizon counterterrorism targeting.

Despite the promises at Doha, many believe that the Taliban and Al Qaeda will retain a close relationship, forged through decades of allied fighting. In contrast, the Taliban and ISIS-K are assessed to be adversaries, who have battled over the past six years for territorial control. Based on these relational dynamics, the United States may find the Taliban to be a cooperative partner against ISIS-K, but not Al Qaeda. Consequently, we forecast four potential options regarding an international legal justification for over-the-horizon strikes against Al Qaeda and ISIS-K in Afghanistan.[2]

Option 1. Host Nation Consent:

If the United States retains a cooperative relationship with the Taliban, they could seek and obtain host nation consent to justify its over-the-horizon operations. A cooperative U.S.-Taliban relationship, relying on mutual self-interest, could open the door for Taliban-facilitated targeting options against ISIS-K in Afghanistan. If the Taliban views ISIS-K as a threat to its control of Afghanistan, it could use the U.S.’ over-the-horizon capability to its advantage. The facilitation spectrum could run from the Taliban offering host nation consent for over-the-horizon strikes against ISIS-K, to providing actionable information on the location of ISIS-K targets. Given President Biden’s recent remarks about hunting down ISIS-K members following the August 26th suicide bombing at the Kabul airport, the Taliban may find an eager partner.

However, even if a cooperative U.S.-Taliban relationship exists, it is difficult to believe that the Taliban would facilitate targeting against its ally, Al Qaeda. Thus, this option raises the intriguing possibility that the United States obtains host nation consent and/or information to support over-the-horizon operations against one terrorist group (ISIS-K) but must invoke the unable or unwilling doctrine described below to target another terrorist group (Al Qaeda). Such a scenario would be unprecedented in the counterterrorism context and would add an intriguing new wrinkle in the already robust dialogue concerning the unable or unwilling doctrine. It is also uncertain whether the Biden administration would consider such an explicit or implicit arrangement with the Taliban as politically tenable.

Option 2. The “Unwilling and Unable” Test and Self-Defense:

Perhaps the simplest and most likely projection is that the U.S.-Taliban relationship will deteriorate and/or never reach a point where the Taliban would consent to (or request) over-the-horizon strikes against Al Qaeda or ISIS-K in Afghanistan. If relations break down and presuming the Taliban retains governance over Afghanistan, the United States will likely invoke the “unable or unwilling” doctrine, in similar fashion to its air campaign against ISIS in Syria. The doctrine provides that use of force in self-defense against a non-State actor in the territory of a third State, without the consent of that third State, may be lawful under Article 51 of the UN Charter. To assert the unable or unwilling justification for use of force in the territory of another State, a victim or responding State must have suffered an armed attack by a non-State actor and the third State must demonstrate that it is unwilling or unable to address the threat posed by the non-State actor. In this scenario, the United States could invoke the unable or unwilling doctrine by asserting that Al Qaeda and ISIS-K have conducted multiple armed attacks against the United States, and the Taliban has demonstrated an unwillingness and/or inability to address the threats these groups pose to the United States.

Though simple, this option may be less than ideal for two reasons. First, while the United States has clearly established its position that the unable or unwilling doctrine permits States to invoke self-defense under Article 51 of the UN Charter, the concept is still relatively nascent and disputed amongst the international community and legal scholars. In contrast, host nation consent to strikes against non-State actors provides a much stronger international legal justification for strikes.

Secondly, this option presumes that the United States would be relegated to building intelligence to support strikes against Al Qaeda and ISIS-K in a denied environment. Information and intelligence concerning the location of Al Qaeda and ISIS-K targets may be more difficult to acquire under these circumstances, thereby potentially enhancing the threat. While the United States would rightly be skeptical of information that the Taliban provides related to ISIS-K location or movements, such “ground truth” leads could conceivably develop into actionable intelligence to support self-defense strikes.

Option 3. Cooperating But Still “Unwilling and Unable”:

Under this scenario, the United States would again rely on the “unable or unwilling” doctrine while simultaneously cooperating with the Taliban on other endeavors. In other words, the Biden administration could attempt to bifurcate its relationship with the Taliban. From a diplomatic or humanitarian angle, it could seek to collaborate to further mutual economic and/or human rights interests. Contemporaneously, the United States could independently target Al Qaeda and ISIS-K sans Taliban involvement, citing the unable or unwilling doctrine.

Though this option offers a hybrid position between the first two options, it is dubious to expect that the Taliban would retain a cooperative relationship to further humanitarian initiatives if the U.S. strikes targets without seeking its consent. Therefore, if the Biden administration were inclined to pursue this option, it may quickly find itself operating within the constraints of the first option above.

Option 4. United Nations Security Council Authorization:

On August 30th, the United Nations adopted Security Council Resolution 2593.[3] The resolution formally condemned ISIS-K’s “deplorable” August 26th attacks in Afghanistan and demanded that Afghan territory not be used to threaten or attack any country. The resolution also reiterated  the importance of combating terrorism in the region, called for enhanced efforts to provide humanitarian assistance, and articulated that the Taliban permit Afghans to freely leave the country if they so desire.

While the resolution did not authorize the use of force or the deployment of peacekeeping forces to Afghanistan, it set expectations for how the Taliban should govern and posture itself against terrorist organizations. If the Taliban fails to adhere to the resolution and prevent Al Qaeda and ISIS-K from metastasizing, the Security Council could consider adopting a Chapter VII, Article 42 resolution, authorizing military action to “maintain and restore international peace and security.” If a Chapter VII resolution were passed, it is possible the United States could cite it as international legal authority for its over-the-horizon operations.

However, a Chapter VII resolution is unlikely given China and Russia’s status as permanent members of the Security Council. Unless the geopolitical landscape dramatically shifts, the U.S. should expect China and/or Russia to veto any resolution authorizing force in Afghanistan. Nevertheless, the United States should petition the Security Council to pass a Chapter VII resolution if ISIS-K and/or Al Qaeda find safe harbor under the Taliban regime.

Forcing the Security Council’s vote represents a potential win-win scenario for the United States. If China and Russia unexpectedly lend support a military resolution, the U.S.’ unable or unwilling self-defense justification for over-the-horizon operations could be bolstered. If China and/or Russia veto, not only might their international credibility suffer due to an unwillingness to address the terrorist threat, the United States could retain its right to conduct over-the-horizon operations without a resolution under the unable or unwilling self-defense rationale. Regardless of the outcome, it will be fascinating to monitor the United Nation’s role in the future of counterterrorism efforts in Afghanistan.


The U.S.-Taliban relationship is clearly fluid and will likely evolve in the weeks and months ahead. While both parties have expressed a willingness to cooperate, the Biden administration’s commitment to over-the-horizon counterterrorism targeting raises some intriguing policy and legal questions. Will the administration retain a cooperative relationship with the Taliban and seek its consent on mutually beneficial over-the-horizon operations against ISIS-K? If so, will the administration be less willing to strike Al Qaeda targets to preserve its cooperative relationship for targeting ISIS-K? Will the Taliban tolerate non-consensual U.S. strikes against Al Qaeda in order to preserve cooperation with the United States for diplomatic purposes? Undoubtedly, the somewhat complicated web of relationships will be factored into the administration’s calculus. As conditions in Afghanistan develop, the horizon should come into better focus.


Major Steve Szymanski serves as an Assistant Professor and National Security Law Course Director in the Department of Law at the United States Military Academy, West Point.

Captain Mike Marchman serves as an Assistant Professor in the Department of Law at the United States Military Academy, West Point, New York.



[1] See also, Eltaf Najafizada, Taliban Call for Good Ties With US After Last Troops Leave Afghanistan, The Print, (Aug.31, 2021).

[2]  The domestic legal justification for continued U.S. strikes against Al Qaeda and ISIS-K will likely continue to be rooted in the Executive Branch’s Constitutional Article II authority, and the September 18, 2001 Authorization for the Use of Military Force.

[3]  The Resolution was adopted by a vote of 13 in favor with two abstentions (Russian Federation and China).