One of the great accomplishments of the last century was the rise of international law. Through the League of Nations, the United Nations and other transnational institutions, the majority of the world’s governments agreed to limits on killing, torture and brutality. International agreements (including the U.N. Declaration of Human Rights, the Convention on the Prevention and Punishment of the Crime of Genocide and the Convention against Torture) bound even the most powerful leaders to disavow forms of violence that had been all too common in the years around the Second World War. International law promised to tame might with the force of right. 

Of course, international law has had its challenges. Some Asian and African countries have condemned the Western-centered assumptions at the core of international law. Others have pointed to the inconsistency of its application. In fact, the United States has promoted and violated international law simultaneously. Americans invoked universal human rights claims in their condemnation of fascist, communist and other tyrannical regimes. At the same time, the United States ignored these claims when made against American military interventions in Vietnam, Nicaragua and Iraq. International law remains a frequent victim of power politics and the prerogatives of dominant states. 

Inconsistency and incompleteness, however, do not negate the deep value of global limits on human brutality. Institutions and documents that condemn repression, genocide and torture create a presumption against those behaviors. They encourage alternative routines and expectations. They raise the costs in reputation and respect for doing things that the international community has so strongly condemned.

Strong condemnations are indeed necessary for the brazen brutality of the Islamic State (also known as ISIS), operating today in Syria and Iraq. This collection of violent insurgents has seized territory and proceeded to express its power with exhibitionist killings of captured foreigners. The Islamic State has now beheaded more than 10 hostages, and last week it went a step further, burning a captured Jordanian pilot to death in a locked cage. The killings are not acts of Islamic faith, which condemns such brutality, but efforts to shock and frighten viewers. 

In this goal, the Islamic State has largely succeeded. The killers have displayed their sadism to the world with slick, cold-blooded videos that threaten more of the same. These videos make most viewers think twice about going to the region, or sending soldiers there. The videos also recruit a small but significant sub-culture of alienated viewers who feel lost and powerless in their current societies. Extreme violence offers the image of power to those who lack power; it promises to give the weak a chance to exact revenge against the strong. The Islamic State videos use blood-curdling brutality to manipulate public emotions and promote more of the same. Without the limits of external force and international law, violence is contagious, feeding upon itself.

There are many things that the United States and its allies in various regions, including the Middle East, are doing to contain and ultimately defeat the Islamic State. Washington has provided military aid, economic assistance and training to numerous groups fighting against the Islamic State. The United States has also used its aerial drone capabilities to identify and kill Islamic State leaders throughout the region. The perpetrators of extreme violence have inspired a strong coalition of regional and global actors supporting the destruction of the Islamic State. The United States is only one government in this coalition, and it can rely on help from many others in the immediate region.

What is missing is a strong affirmation of why fighting the Islamic State is a compelling mission for believers in a world of law, not arbitrary power. The greatest threat the beheadings and cage burnings pose is to undo the work of the last century. If this behavior can continue with minimal reprisal, then it becomes normal again, and others will follow. Some evidence of law-erosion is already evident in Russia and other countries where dictators are closely watching events in the Middle East, to see what tools they might also be able to deploy against their opponents. The historical record shows that tyrants are dangerous copy-cats. 

Fighting the Islamic State requires a broad and full-throated condemnation of its horrors. This is a battle for law, for progress, and even for “civilization” – defined in this case as the widely accepted limits on violence against individuals. These limits allow space for the flowering of freedom, self-governance and innovation that made the last century such a liberating moment for many groups around the world. Without the strong defense of limits on human brutality, we will all be brutalized again. 

The world has not escaped its anarchic and violent characteristics, and the United States is responsible for numerous atrocities of its own, but the sadistic inhumanity of the Islamic State destroys the very foundations for international peace and justice. As citizens, we must demand that our government affirm our core values in this fight, even as our leaders wisely search for the most effective ways to destroy the Islamic State from a distance. Clarity of purpose must accompany prudent military and diplomatic tactics. Everyone must know the stakes for humanity in the recent horrors, and why they cannot continue.

Suri is a professor in the LBJ School of Public Affairs and the Department of History. Follow Suri on Twitter @JeremiSuri