Just War Theory and the End of the Afghanistan War

On June 27, during the first Presidential Debate of 2024, former President Donald Trump referred to the US military withdrawal from Afghanistan as “the most embarrassing moment in the history of our country.” Not only is this comment hyperbolic; it is also wrong in spirit. The concepts and principles of just war theory show that President Biden’s decision to end the Afghanistan War in 2021 was a wise and just choice for which he should be praised, not blamed.

Just war theory is the network of concepts, principles, and logical moves that dominate moral reflection on warfare in the West. The ideas and values in this theory grew from Christian roots, starting with St. Augustine, into modern secular forms, such as the work of Hugo Grotius. At its heart, just war theory makes a strong distinction between jus ad bellum, which includes criteria that establish justice in going to war, and jus in bello, which includes criteria about justice in combat once belligerence has begun. Criteria from both categories can help us see the justice and wisdom of Biden’s decision to end the war in Afghanistan.

First, under the heading of jus ad bellum, the just war tradition asks people to think about several moral factors when deciding to enter into armed conflict. One of those factors is “proper authority.” According to this criterion, a competent political authority is required for engagement in belligerence to be just. One reason why a competent political authority is required, according to many just war thinkers, is that once belligerence has begun, it must be directed by a leader who can control, limit, and end it.  Being able to end a war is one of the central reasons why proper authority is required in the first place. Without the ability to end a war, the political authority would tacitly allow and be responsible for protracted and unnecessary death, suffering, and destruction. One way a political authority can show its competence is by recognizing when the cessation of belligerence is required and making the decision to end it, however difficult that decision might be.

The idea of “reasonable hope for success” is another criterion in the category of jus ad bellum that illuminates the difficult decision to end the Afghanistan War. According to just war theory, engagement in belligerence requires prudent reflection on the war’s aims and whether or not they are attainable. If the war’s aims are not attainable, the hostilities will be nothing more than a futile waste of precious blood and treasure. The early modern Spanish theologian Francisco Suarez, for example, wrote that “a prince is obliged to make as sure as possible of victory. He should measure the likelihood of victory against the risk of loss, weighing everything up to see whether the calculation is decisively positive.”  

In 2021 it was time to end the war. At that time, and even before then, there was no clear path to success, and thus no reasonable hope of victory. As Wesley Morgan explains in his Colby-Award winning book, The Hardest Place: The American Military Adrift in Afghanistan’s Pech Valley, by 2021 the aim of creating an Afghan National Army that merited the people’s trust was clearly not a viable goal. Despite deep investments in its institutions and personnel made by the American military, the ANA was unable (and apparently, at times, unwilling) to provide the people with security against the Taliban.  Even worse, the aims of the war were not clear from much earlier moments. Morgan quotes Lieutenant Colonel Joseph Ryan as saying in 2010, “Why are we here?...Are we building a nation? Are we chasing terrorists? I read the same news as you do, and it doesn’t always seem very clear.”  The most clearly achievable aim of the war was holding Osama bin Laden accountable for the atrocities of September 11, 2001, and that goal was accomplished in May of 2011. For the ten years after that, the American military learned that other aims such as establishing a democratic regime, training a national security force, and/or winning the hearts and minds of the people of Afghanistan were not achievable ends. Those ten years were incredibly costly. At 20 years, the Afghanistan War was the longest in US history. We lost 6,247 American lives in the Afghanistan War, which amounts to an average of more than 312 deaths per year. The death toll for the civilians of Afghanistan was much higher, at 46,319, and this number should be considered just as much as the deaths of American military, Department of Defense civilians, and contractors are. We spent $2.31 trillion on the Afghanistan War, which amounts to an average $115.65 billion per year. The principles of proper authority and reasonable hope for success require that, once a nation realizes these incredible costs and the low probability of success, it ceases the belligerence.

Second, the distinction between jus ad bellum and jus in bello categories allows us to see that we can make judgments about the justice of the war and its cessation independently of judgments about how it was fought. While considerations of the justice of going to war prioritize factors such as just cause, proper authority, reasonable hope for success, and others, reflection on just conduct in war considers the actions of combatants, especially whether or not they intentionally target civilians. Morgan’s book shows that US servicemen and women did their best to distinguish combatants from non-combatants during the Afghanistan War even though doing so was extremely difficult. Indeed, the US military and the ANA were unable to win hearts and minds and provide security to the people of Afghanistan precisely because this was an insurgency war. When combatants purposely blend in with civilian populations, civilian deaths are inevitable even with the most disciplined and prudent precautions. Civilian deaths, in turn, make winning hearts and minds impossible and lead people to believe that security is best sought elsewhere. In short, we can say that the American military fought well in the Afghanistan War while also admitting that the war’s goals were never well articulated, and therefore it was difficult to see a viable path to success.

President Biden was right to end the Afghanistan War when he did. Could the war’s cessation have been better orchestrated tactically and logistically to minimize deaths and destruction? Of course. But a clean exit was never a possibility, and the war needed to end. Instead of being blamed for ending the war, President Biden should be praised for it.

About the Author

Dr. Daniel A. Morris is an associate professor of philosophy, religion, and ethics at Norwich University. He writes and teaches about just war theory, race, and American politics.

¹ See, for example, Thomas Aquinas, The Summa Theologica (Notre Dame, I.N.: Christian Classics, 1981), IIa IIae, Q. 40; Francisco de Vitoria, Francisco de Vitoria: Political Writings, ed. Anthony Pagden and Jeremy Lawrence (Cambridge, UK: Cambridge University Press, 2001), 300–304, 326–27.

² Francisco Suarez , The Three Theological Virtues, Faith, Hope, and Charity, in Oliver O’Donovan and Joan Lockwood O’Donovan, eds., From Irenaeus to Grotius: A Sourcebook in Christian Political Thought (Grand Rapids, M.I.: Eerdmans, 1999), 740.

³ Wesley Morgan , The Hardest Place: The American Military Adrift in Afghanistan’s Pech Valley (New York: Random House Trade Paperbacks, 2022), 259, 293.

^4. Morgan, xxii.