(Editor’s Note: This is the first of three articles on how the lines have blurred between U.S. military operating procedures for use of force in hot war zones versus outside areas of active hostilities and how the executive branch and Congress might better govern operations going forward.)

Mohammed Atef, al-Qaida’s military chief at the time of the 9/11 attacks, appears to have been one of the first casualties of America’s remote-killing campaign. A Predator drone reportedly targeted and killed him in November 2001 during the U.S. invasion of Afghanistan. A year later, the United States reportedly executed its first drone strike outside a traditional battlefield, killing an al-Qaida commander in Yemen, Abu Ali al-Harithi, who was involved in the October 2000 attack on the USS Cole.

As a legal matter, the United States did not then, nor does it now, make any distinction for purposes of international and domestic law between traditional war zones like Afghanistan or Iraq where U.S. forces have been deployed in large-scale combat operations, and non-traditional areas of conflict such as Yemen where U.S. forces have been largely absent or mainly supporting partner nations. As a matter of policy, however, the U.S. government has observed different practices when striking targets in traditional versus non-traditional battlefields, and it has developed a different and more rigorous set of guidelines to govern the use of force in the latter.

President Barack Obama’s decision to put forth a set of rigorous guidelines in 2013 for strikes outside of traditional battlefields represented the zenith of U.S. efforts to define two sets of rules: one for hot war zones (“areas of active hostilities,” in the parlance of Obama’s guidelines), and another for countries where U.S. forces were not as intensively involved in conflicts against terrorist groups. Press reports suggest that the Trump administration largely retained the bifurcated system, even as it moved to loosen the standards for strikes outside hot war zones.

But in the past several years, what once seemed like relatively clear divisions between more “active” and less active battlefields have largely blurred, such that across theaters of operations we now find ourselves in a muddy middle where the nature of the threat, the operating environment, and U.S. operations look increasingly similar. We need a new framework to govern operations going forwardthat allows for the effective pursuit of our terrorist adversaries while also ensuring that U.S. operations remain discriminate, precise, and bounded within the rule of law.

Clear Divisions

With a few notable exceptions, it was relatively easy to distinguish traditional and non-traditional battlefields from one another for roughly a dozen years after 9/11. Afghanistan and Iraq were in the first category: within less than two years after 9/11, the United States invaded and overthrew governments in both countries, and in the aftermath, insurgents and terrorists fought against the occupying forces. New, U.S.-backed governments formed, and the U.S. military remained engaged in combat operations for years. It also provided a broad range of operational support – such as training, equipment, intelligence, embedded combat advisors, and even air support – to partner forces to build their capacity to shoulder more of the fight against terrorist adversaries.

The United States remained a powerful actor in each country and essential to the gains against insurgents and terrorists. U.S. forces took aggressive and wide-ranging actions, within the laws of war, to defeat the enemy. More than 100,000 U.S. and coalition forces were deployed to Afghanistan and to Iraq at different times to conduct full-scale combat operations against insurgents who engaged in a spectrum of violence, sought to hold and govern territory, and in some cases, threatened the United States or its interests outside of these theaters.

Outside the active war zones in Afghanistan and Iraq, the United States confronted a panoply of terrorist organizations across the Middle East, Africa, and South and Southeast Asia. Many of these groups were unable to take, hold, and administer territory because they confronted host nations that were sufficiently strong in terms of their military, law enforcement, and intelligence capacities and committed to counterterrorism. But there were exceptions, most notably in Somalia, Yemen, Pakistan, and the Sahel, where either the terrorist threat was too strong for the host nation to handle or where the host nation lacked the political will to address the threat.

Dealing with international terrorist threats emanating from non-traditional battlefields where the United States did not have a considerable military footprint forced U.S. policymakers to make tough decisions about how to work with partners when possible, and how to work around them when necessary. The United States had various instruments at its disposal, two of which had major ramifications for the use of force: special operations forces, who primarily trained and advised partner forces, but occasionally conducted counterterrorism raids, and targeted air strikes.

Host nation forces, even those with limited capabilities, were at the tip of the spear in most places, and bore the burden of combat operations against shared terrorist threats. Over time, it became clear that the most effective model for building a partner military’s capacity in these environments, at least in the short term, called for much more aggressive operational support, with embedded U.S. advisors providing intensive assistance, accompanying partner forces on operations, and supporting local forces with unique U.S. capabilities like airlift, intelligence, and air strikes.

The historical record suggests that this model, although it could be effective when  implemented, often failed to yield positive results that had staying power. Moreover, even in the short term, it was often difficult to execute such a full suite of operational support in the places where it was needed. In Pakistan, for example, a robust and visible U.S. presence was not acceptable to local governments or their populations. In other countries, like Somalia and Yemen, concerns over the risk to U.S. forces often precluded more intensive models of engagement. In few places was the United States able to provide the higher-level institutional capacity building support necessary to reinforce gains made by tactical forces. Even when the United States could conduct full-scale capacity building programs, the progress of partner forces was often slow due to a variety of resource and political constraints.

The quickly growing capabilities of still-nascent remotely piloted drone technology enabled U.S. policymakers to use air power against terrorist groups that directly threatened Americans and that partner nations either could not or would not combat effectively. Drone strikes could be conducted without risk to U.S. forces and reduced the risk to local populations that are implicated in ground operations. In Yemen, for example, direct action provided the Obama administration with a way to augment Yemeni forces, which were undergoing intensive capacity building efforts with U.S. advisors, as well as to act alone – though with the consent of the Yemeni government –  when necessary. Targeted air strikes successfully removed a number of senior and experienced al-Qaida in the Arabian Peninsula (AQAP) leaders and helped maintain pressure on the group at times when the host nation was preoccupied with other security threats and political challenges. Yet new leaders emerged.

Direct action strikes were never intended as a holistic solution. Nevertheless, as these strikes became more precise and easier to launch, the U.S. government came to rely more on them to combat foreign terrorist organizations in countries where U.S. forces were not on the ground in sufficient numbers or deployed for combat purposes. Non-governmental organizations that track U.S. counterterrorism operations noted a massive surge in air strikes outside areas of active hostilities from 2009 to 2012. According to the Bureau of Investigative Journalism, for example, the overwhelming majority of these occurred in the Afghanistan-Pakistan border region where the Taliban, Haqqani Network, and al-Qaida operated, followed by Yemen. The United States also conducted a smaller number of strikes against the al-Qaida-aligned al-Shabaab in Somalia. As drone strikes became the weapon of choice, the need for clearer parameters governing their use increased.

A Framework for a New Kind of War: Obama’s Presidential Policy Guidance

Shortly after beginning his second term in 2013, President Obama issued a new set of rules in the form of Presidential Policy Guidance (PPG) for taking direct action, including lethal force, against terrorist targets outside areas of active hostilities. By establishing a separate set of standard operating procedures for these countries, the PPG distinguished them from areas of active hostilities (or hot war zones) like Afghanistan.

The United States maintained that it was at war with al-Qaida and its “associated forces” wherever they may operate, in Afghanistan as in Yemen, and that the international legal basis for its operations was the same. Nevertheless, the PPG’s guidelines set much higher standards for lethal targeting in non-traditional battlefields than were legally required under the law of armed conflict (LOAC). Specifically, the guidance required that lethal force only be used against terrorists that posed a “continuing, imminent threat to U.S. persons.” Even then, force could generally be employed only when capture was assessed to be infeasible and the relevant operational commander could assess with near certainty that civilians would not be harmed in the operation. The bar was set significantly higher than LOAC, which does not specifically require “near certainty” that civilians will not be harmed. Rather, it requires that civilians are not made the target of an operation and that any harm to civilians and civilian objects is not “excessive” as compared to the anticipated military advantage of the operation.

The PPG’s provisions echoed, but did not formally commit to, certain aspects of international human rights law, particularly those pertaining to the need for an imminent threat to trigger lethal action and those setting the default position in favor of capturing a target over lethal operations. It also addressed, again without legal commitment, the concerns of some partner nations that took the view that outside of active battlefields a new analysis as to whether a state may resort to armed force (under the jus ad bellum) is required for each strike.

Critics were quick to argue that the United States did not always live up to its own lofty standards, particularly when it came to preventing civilian casualties and exhausting the possibility of capture before taking action. Many of these same critics also offered support for the idea of imposing a more restrictive framework on U.S. counterterrorism operations outside traditional battlefields –where debates occurred over whether the more permissive targeting rules found in LOAC extended at all – and saw the PPG as a strong first step in that direction. The guidance rejected the employment of a warlike strategic frame for lethal targeting in favor of a constrained set of rules for use outside of traditional battlefields.

Distinctions Never Really Clear

In truth, the bifurcated worldview of the PPG was never as clean as depicted. The guidelines imposed a singular framework on a messy world: numerous countries fell under the umbrella of non-traditional battlefields and they were hardly homogenous. In several such locations, the host nation had or was still engaged in intense combat operations against terrorist groups – what an outside observer might describe as “active hostilities” – at the time of the PPG’s release. This highlighted an important point about the phrase “areas of active hostilities”: it was not defined purely by the nature of a given conflict, as it also reflected the goals the United States was pursuing in a specific place.

Indeed, the government’s own definition of areas of active hostilities (released in December 2016) states: “The determination as to whether a region constitutes an ‘area of active hostilities’ does not turn exclusively on whether there is an armed conflict under international law taking place in the country at issue, but also takes into account, among other things, the size and scope of the terrorist threat, the scope and intensity of U.S. counterterrorism operations, and the necessity of protecting any U.S. forces in the relevant location.”(emphasis added)

Nevertheless, in practice, the PPG’s distinction between areas of active hostilities and non-traditional battlefields still reflected a real operational difference between places where U.S. forces were fighting in large numbers against robust insurgencies, and relatively more stable countries where partner forces were clearly in the lead but unable or unwilling to apply sufficient pressure on terrorist groups.

The PPG was issued as the U.S. military was coming off of a series of successes in the two years before its release. U.S. forces killed Osama bin Laden in 2011, Yemeni forces wrested substantial territory from AQAP control in 2012, and Somalia was making steady progress after African Union forces there dealt al-Shabaab a series of blows. In his re-election bid, President Obama stated that core al-Qaida had been “decimated in the FATA,” referring to the federally administered tribal areas of Pakistan. Thus, the PPG reflected a bit of triumphalism and an aspiration that the terrorist threat would continue to diminish while U.S. partners would keep growing in strength.

Still, these operational successes hardly constituted a new stability in counterterrorism theaters. Yemeni government and African Union forces in Somalia, for example, still continued to engage in bloody clashes with al-Qaida-linked militants. The decimated al-Qaida continued to threaten U.S. interests, and the U.S. government expected Ayman al-Zawahiri to attempt to avenge his predecessor’s death.

But these seemed to be relatively small aberrations in an overall positive trajectory in the fight against al-Qaida and associated forces. The United States had made substantial gains in its counterterrorism fight by 2013, and it seemed appropriate to build a framework for a world in which U.S. partners were increasingly out front and the United States only used force outside areas of active hostilities in response to the gravest direct threats. The major counterterrorism theaters seemed to be arcing toward the administration’s framework. Instead, in the years following the PPG’s release, terrorist groups gained momentum in numerous countries that qualify as non-traditional battlefields.

(The next article in this series examines the evolution of the U.S. government’s procedures for use of force outside areas of active hostilities in practice. The third and final installment will propose a framework for going forward.)

IMAGE: A US Predator unmanned drone armed with a missile stands on the tarmac of Kandahar military airport on June 13, 2010. (Photo by MASSOUD HOSSAINI/AFP/Getty Images)