Opinion: The ‘just war’ doctrine of proportionality does not work with terrorists

The hoary doctrine of “proportionality” from the “just war” theory is being sorely tested by the wars in the Middle East and Ukraine.

The premise of this theory , as first expounded in the West by Saint Augustine and later elaborated on by Thomas Aquinas, is that the use of force by governments against other states, generally morally prohibited, is justifiable under certain circumstances. It is about defensive war, undertaken in response to acts of aggression by others.

A key element in just war is the notion of proportionality — that the response to aggression must be in a certain sense symmetrical. The force used must not exceed what is necessary.

In the modern age, the degree of military destructiveness has exponentially expanded with the advance of technology. The use of certain weapons systems, most notably weapons of mass destruction — nuclear, biological and chemical — inherently violates the requirement of proportionality. Their use is so horrific that such weapons have generally been prohibited, deemed to constitute war crimes or crimes against humanity.

But beyond the hardware of weapons systems, the operational techniques used in warfighting can also be considered criminal in nature, such as the targeting of civilians or deliberately putting them in harm’s way. Such criminal acts have been commonplace in the wars being waged by terrorist states and groups in the Middle East against Israel and by Russia against Ukraine.

As these two friends and strategic partners of the United States have fought valiantly to defend their populations and territory, the Biden administration has repeatedly urged restraint and “proportionality” in their respective responses. In Gaza, thousands of civilians have reportedly been killed as Israel responds to the October 7 massacre by rooting out and destroying the Hamas terrorists who perpetrated it and vow to repeat it. Would proportionality limit Israel just to identifying those individuals who committed the heinous acts and limiting its operations to punishing them? Or would a proportional response be the destruction of the entire organization, which has promised to repeat October 7 again and again until the state of Israel is wiped from the map?

When Iran fired hundreds of missiles into Israel in April and the air defense system of Israel, with U.S. help, successfully brought them down . Washington then cautioned Israel against going further in retaliation, arguing that Israel should just “take the win” and not inflict greater punishment on Tehran for its brazen attacks.

Similarly, in Ukraine, the Biden administration has repeatedly withheld weapons systems that the Ukrainians could put to good use in defending and counter-attacking against Russia’s aggression. It has also prohibited Ukraine from using U.S. and NATO weapons to strike deeper into Russia at facilities from which Vladimir Putin is launching attacks on Ukrainian civilians, cities and critical infrastructure.

Last week, in response to Israel’s destruction of much of Hezbollah’s leadership, Iran launched another massive missile attack on Israel, firing twice as many missiles as it did in July. Israel has promised a decisive counter-attack, and there has been widespread speculation as to how widespread Israel’s targeting will be — Iran’s military installations? Its oil production infrastructure? Its nuclear weapons development facilities? Or even the Iranian leadership itself?

Given Iran’s sponsorship of Hamas, Hezbollah, the Houthis and other terrorist groups, all dedicated to Israel’s destruction (as is Tehran itself), it can plausibly be argued that all the hypotheticals above would constitute proportional responses to the existential threat Iran poses to Israel.

The Biden administration’s calls for restraint are not based on theological or philosophical views of proportionality and just war theory, but on very pragmatic concerns about escalation and a wider regional war. The president fears the potential to drag the U.S. into conflict with Russia, which has supported Iran and its terrorist proxies. On Ukraine, President Biden has more than once expressed fear that greater U.S. involvement could trigger World War III .

The deficiency in the West’s view of proportionality is in its failure accurately to define the action to which the West’s response is to be proportional. Is it to be narrowly considered as a particular military operation or the larger strategic objective of which it is a part and which it serves?

Joseph Bosco served as China country director for the secretary of Defense from 2005 to 2006 and as Asia-Pacific director of humanitarian assistance and disaster relief from 2009 to 2010. He is a nonresident fellow at the Institute for Corean-American Studies and a member of the advisory board of the Global Taiwan Institute.

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