This past weekend the lone American prisoner of war from the war in Afghanistan, captured by insurgents nearly five years ago, was released to American forces in exchange for five Taliban detainees held at Guantánamo Bay, Cuba. The five detainees included two senior militant commanders said to be linked to operations that killed American and allied troops as well as implicated in murdering thousands of Shiites in Afghanistan.

As American Christians we should pray for the released Taliban leaders and be thankful this young soldier will be reunited with his family. But we can and should also use this incident to reflect on the ethics of prisoner of war exchanges.

The Purpose of Capturing Prisoners

In the Marine Corps Doctrinal Publication Warfighting, there is one sentence that succinctly explains the goal of warfare: “The object in war is to impose our will on our enemy.”

The role of military forces in warfare is therefore simply to provide “organized application or threat of violence” to make the enemy conform to a nation’s will. When militaries clash on the battlefield, the overall objective on each side is to incapacitate this threat in order to prevent the enemy from being able to impose their will upon your side. Generally speaking, the primary means of carrying out this task of incapacitating the enemy is by killing, maiming, or capturing their human forces.

If you kill an individual enemy, you’ve removed one troop from the fight. But if you maim an individual, other troops will likely come to their aid, removing multiple threats (at least temporarily). The third, and most humane, approach is to capture as many of their forces as possible without having to kill or maim.

Even though the capture of large number of prisoners can produce logistical problems, this is still one of the most direct way to impose one’s will on the enemy. During the Gulf War (1991), for example, thousands of Iraqi soldiers surrendered to American forces, a move that prevented greater losses of life and considerably shortened the conflict.

Why Prisoners are Exchanged

Prisoners of war are usually held until the end of hostilities to prevent them from returning to the fight. If they are unable to fight or lead troops in combat, there is no reason to keep them prisoners. Under the Geneva Conventions, any prisoner that is seriously wounded or seriously sick and cannot contribute to the war effort and is entitled to be repatriated to their home country or internment in a neutral country.

In some wars during the eighteenth and nineteenth centuries (e.g., the American Revolutionary War, the Napoleonic Wars, the War of 1812), able-bodied combatants of similar rank would be exchanged even while the war was ongoing. In later wars, however, most releases and exchanges only occurred after the fighting had ended. The reason is that there is no obvious benefit to swapping out soldiers. If combatants on both sides are reentering the ranks and returning to the battlefield, they are only delaying the primary objective of warfare.

While this is a prime strategic reason for not engaging in prisoner swaps, it can also serve as moral justification.

The Moral Factor We Should Consider: Average Lethality

Most individual combatants have a negligible effect on the outcome of a war. In fact, the average individual soldier has a limited degree to which they themselves are capable of causing injury or death on the battelfield. To quantify this effect, let’s call this ability to maim and kill the Average Lethality Factor (ALF). In modern wars, the ALF is less than 1 since few individual soldiers actually kill or maim in combat. But let’s take a high estimate and say that it can range from 0 to 10, which would make the median ALF a factor of 5 (that is, the average solidier could possibly kill five enemy combantants during the course of a war). This means that if returned to combat, the average individual prisoner of war would be able to maim or kill an average of 5 enemy combatants. When exchanging prisoners, a nation would therefore want to swap those with similar ALFs. Someone with an ALF-1 would be traded for other ALF-1s, ALF-10s for other ALF-10s, etc. A nation would not want to intentionally release prisoners who would upset the overall balance of the war effort in their enemies favor.

But what if you had a prisoner of war who, because of experience or leadership ability, was able to have an ALF multiplier? Say, for instance, that during World War II, the Nazis were somehow able in 1944 to capture Gen. Dwight D. Eisenhower, the Supreme Commander of the Allied Forces in Europe. If the Nazis were unaware of Eisenhower’s reputation, they might grade him as having an ALF-1. But if they knew he was the architect of early war efforts, they might grade him as an ALF-50,000. His experience and knowledge makes him, even as an individual, an exceptionally dangerous prisoner. They would need to get 50,000 Nazi POWS back in exchange for this one man—though even then, it might not be worth the trade if Eisenhower caused them to lose the war effort.

The Moral Calculus

From an objective moral standpoint, our support of a prisoner swap should depend primarily on which side is gaining a strategic advantage. Even if we oppose the war in general, we should want the side with the most moral justification for imposing their will on their enemy to gain the advantage. If Nation A has the most just cause (relatively speaking), we should favor them making prisoner swaps when the ALF imbalance is in their favor. If the imbalance is in favor of Nation B, we should oppose the trade, even if we support the emotional reasons for the exchange.

In the latest exchange the U.S. swapped five high-risk, high-ranking Taliban officials for Army Sergeant Bowe Bergdahl. From an emotional and individual perspective some Americans could say it was a good trade since the life of one American is worth more than a hundred Taliban. But we have to consider the future lives lost. Sgt. Bergdahl has an ALF of zero, since he will not be returning to combat. The five Taliban, however, should be rated—at a minimum—an ALF-1. So the swap was not just for the life of one American, but also for the potential loss of life of at least 25 Americans or allied Afghanis.

Does this exchange have the potential for a moral imbalance and greater loss of American and allied lives? Presumably it would, though it’s likely the Obama Administration made a similar calculation, was aware of the danger, and believed such an outcome could be avoided. Hopefully, the administration knows more than we do about true threat these Taliban leaders pose and have taken steps to neutralize that danger.

When Americans are held as prisoners of war, many factors, ranging from the emotional to the political, can influence the decision to exchange them for enemy combatants. While we can create criteria for making moral judgments in such situations, we should also be sympathetic to those who have to make the final decisions. Instead of be too hasty in our criticisms, let’s pray our leaders were guided by prudence, wisdom, and God’s leading.