The Future Character of War and the Law

by | May 5, 2021

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In 2018, then Army Chief of Staff General Mark Milley wrote that socio-economic, political, and technological changes will “revolutionize battlefields unlike anything since the integration of machine guns, tanks, and aviation which began the era of combined arms warfare.” In fact, these changes are well underway with emerging technologies, non-State actors, and new domains, such as cyber and space, increasingly impacting combat operations. Ubiquitous sensors may compel forces to find new ways to surprise adversaries and hide in plain sight. The speed, quantities of information, and use of technologies such as artificial intelligence and machine learning will likely transform decision-making and alter how we fight. In the future, the shaping phase before a conflict “starts” may be critical, blurring the line between peace and war. Meanwhile planners and strategists have turned attention toward great power competition. Consequently, States are intensely focused on thinking “deeply and clearly about the problem of armed conflict in the future”  in order to evolve and adapt to the changing character of war.

A part of this broader thought exercise is to determine how and if the law of armed conflict (LOAC) may need to adapt to future hostilities. Will existing law be called on to adjust to operational realities? If so, how? Is there a risk of fragmentation? Could neglected or disused legal doctrines find new relevance in future conflict? Although the law of armed conflict has traditionally been a legally reactive body of law responding to lessons from previous wars, can we take a prospective approach to prepare for challenges a future battlefield may present?

These are questions that the Lieber Institute for Law and Land Warfare has been thinking about for several years. In 2019, Lieber hosted a workshop on the Future of the Law of Armed Conflict. That event produced a forthcoming book published by Oxford University Press as part of the Lieber Studies Series. The workshop convened practitioners and academics to consider how the law of armed conflict will operate in 2040. This earlier work sets the stage well for Lieber’s current and upcoming work and therefore warrants renewed attention. Below are observations informed by this work and the upcoming Lieber Studies Series volume.

But first, a few words on the Lieber Institute’s new partnership with Army Futures Command.

This year, to delve deeper into the realities of future conflict and the law, Lieber is participating in Army Futures Command’s wargame and Future Study Program (or Unified Quest, the Army’s Title 10 wargame). This includes seminars, tabletop exercises, and wargames geared toward developing a new operational-level concept of warfare for 2035 and beyond. The focus is how the Army could operate, how it could be equipped, and how it could be organized in a contested environment and against a peer adversary that will likely be matched or overmatched in capabilities in 2035 and beyond.

The Lieber Institute’s role is to think through possible legal implications of anticipated changes in the character of future war. To this end, Lieber and Army Futures Command held a kick-off event on The Future Character of War and the Law of Armed Conflict in April that emphasized the importance of thinking deliberately, thoughtfully, and responsibly through the legal implications early on. Army Futures Command input enabled the Lieber Institute to highlight a number of legal issues that we think need more consideration at this early stage.

As Lieber moves forward with its partnership with Army Futures Command, we will continue to develop these and more issues in further depth. A more extensive legal conference will be held in September to explore key legal concepts.

Some Questions about the Future Law of Armed Conflict

To frame future discussion, some of the questions that arose during Lieber’s past work and are in the upcoming Lieber Studies Series volume remain relevant. Three underlying questions in particular are useful to keep in mind as we move forward: Will existing law change? Will the law move toward fragmentation? What is the value of present and past law as we move into the future?

Will Existing Law Change?

Although dramatic changes in technology, power struggles among States, and the rise (or decline) of the influence of non-State actors will undoubtedly alter the character of future armed conflicts, what remains unclear is whether the law will need to evolve with these changes. For example, the legal problems associated with using hypersonic weapons are not entirely new and the traditional principles—as well as other relevant existing rules—may adequately regulate this emerging technology. On the other hand, the way in which these technologies may be used combined with other technologies could present legal challenges.

Of course, historically, new technology often prompts efforts to regulate through treaties. Air power, chemical or bacterial weapons, or nuclear weapons are but a few examples. But the reconstitution of a possible great power conflict makes agreement upon new globally accepted treaties unlikely—at least barring major catastrophe (an important caveat that could be a game-changer).

Resistance to developing conventional law may push observers to emphasize State practice in order to claim new customary international law. If true, this will cause friction between the idea that States make law and an unwillingness on the part of States to let law outstrip their interests. Further, relying too heavily on customary international law, especially if based on thin State practice, risks devaluing this method for formulating international law. As I have previously written, “[customary international law] development is difficult and raises several problematic questions. For example, how does the international community reconcile inconsistencies in the practice of States? Is it possible to deduce specific rules from general principles? When is a State providing clarity on a view versus making a statement of opinio juris?”

Finally, it appears that non-State actors will increasingly influence the development of LOAC. Private actors already play an important role in space, control many of the data centers required for developing artificial intelligence, and engage in State-like behavior (The Syrian Democratic Forces detaining members of ISIS for example). While creating international law remains within the purview of States, non-State actors’ real-world power gives them a voice in how the law may develop. As a result, any future developments in LOAC, if it is to remain effective, must account for non-State actors’ interests.

Will the Law of Armed Conflict Fragment?

Common ground in applying LOAC is still possible as demonstrated in coalition operations—for example 68 States worked together in the counter-ISIS campaign. However, a consensus on how LOAC should develop and should be interpreted is unlikely for several reasons. First, the technological “haves” and “have nots” increasingly view warfare and legal obligations differently. Second, as clearly indicated by the ongoing paralysis of the United Nations Security Council, States have dissimilar objectives and world views. Third, several States, often those that were previously marginalized, increasingly have influence.

These combined trends make it difficult for States to agree on how LOAC should govern future warfare. For this reason, legal interoperability for like-minded States will remain immensely important. Again, this may be through coalition operations or, as is increasingly the case, through regional actors such as the African Union, the Association of Southeast Asian Nations (ASEAN), or the European Union. Additionally, this pluralistic approach to LOAC will ensure enforcement remains highly decentralized as States are unlikely to agree to any type of broad accountability mechanisms or to make their militaries subservient to international oversight. This is, unfortunately, best illustrated by Russia’s decision to withdraw from the Article 91 procedures of Additional Protocol 1 to the 1949 Geneva Conventions and its power to investigate war crimes against civilians.

Perhaps the move away from a global consensus on LOAC interpretation and development is a natural consequence of the end of the Cold War with its efforts to build an international society. Or, perhaps it is driven by national interests and a growing disdain for international law generally. Whatever the reason, it appears States will continue to compartmentalize their perspective on LOAC with yet unforeseen consequences.

What is the Value of Forgotten Aspects of the Law and of Present Law?

However, as is often the case when looking into the future, there is risk of overestimating change. This is especially true when looking ahead to the near-term future. Fifteen to twenty years is not a very long time for the evolution of LOAC. It is very possible that the demise of the international community is overblown, and States will continue to find it in their interest to promote a shared view of LOAC. Maybe, when looking back we will find that the current law held up well under the stress of the modern battlefield. And perhaps we will find that too much emphasis was placed on the impact of technology and not enough thought given to political processes and power.

Additionally, as Patrick Henry once said, “I know no way of judging of the future but by the past.” It is helpful to look to traditional, albeit relatively forgotten, aspects of the law to help resolve future issues. For example, the law of neutrality, which originally emerged to address the conflicting interests of belligerent and neutral States, is again finding relevance as military operations rely more on cyber and space assets. Similarly, the law of belligerency may have contemporary usefulness in addressing the various problems that arise by the extensive involvement of non-State actors in armed conflict. In other words, there may be great value in revisiting neglected LOAC doctrines when searching for answers to the legal questions that arise from future military operations.

Concluding Thoughts

Regardless of what the future holds for LOAC, it is clear that a multidisciplinary approach is crucial. Working with Army Futures Command and their multidisciplinary consortium of people—to include operators, scientists, technology experts, strategists, etc.—allows for a realistic picture of the complexities and challenges that warfighting in 2035 and beyond will undoubtedly present. Moreover, academics and practitioners must continue to work together. This partnership is critical for ensuring LOAC is both practical in implementation yet has undergone a critical and objective analysis. Active engagement between these two communities—and continued collaboration with experts across disciplines—is therefore of utmost importance as we consider the future. Otherwise, there is risk that LOAC becomes increasingly anachronistic and incapable of regulating future armed conflicts.


Shane Reeves is a Colonel (Promotable) in the U.S. Army. He is Professor and Head of the Department of Law at the United States Military Academy, West Point, New York, and Co-Director of the Lieber Institute for Law and Land Warfare. He will serve as the United States Military Academy’s next Dean of the Academic Board.