Illustration by Tom Bachtell

Early in 1987, Saddam Hussein, the Iraqi President, decided to clear out scores of Kurdish villages, in order to undermine separatist rebels. He asked Ali Hassan al-Majid, a general and a first cousin, to lead the project. In tape recordings later produced by Iraqi prosecutors, Majid told Baath Party colleagues that the novelty and the terror of chemical weapons would “threaten” the Kurds and “motivate them to surrender.” On April 16th of that year, Iraq became the first nation ever to drop gas bombs on its own citizens; the gassing campaign lasted two years and killed thousands of people. “I will kill them all with chemical weapons!” Majid told his colleagues. “Who is going to say anything? The international community? Fuck them! The international community and those who listen to them!”

Two weeks ago, on August 21st, a poison-gas attack killed more than fourteen hundred civilians in the suburbs of Damascus, Syria’s capital. President Obama, in fashioning a response, has been burdened by the United States’ recent history with Iraq. The Administration of Ronald Reagan stood by as “Chemical Ali” waged his campaign against the Kurds. Fifteen years later, to justify an invasion of Iraq, the Administration of George W. Bush infamously claimed that Saddam Hussein still possessed chemical and biological arms. It soon became apparent that Saddam had abandoned them. That tragic war has rightly raised the standards of proof that Obama must meet to credibly propose military action in the Middle East, particularly if the casus belli concerns unconventional arms.

The Obama Administration, Britain, and France say there is little doubt that Syrian President Bashar al-Assad is responsible for the recent slaughter, although they concede that the evidence is not airtight. The video imagery of the aftermath is indelible: unbloodied corpses, including toddlers’, in white shrouds; hospital patients choking and drooling. The chances that rebels were responsible seem slim to nonexistent. Yet last Thursday Britain’s Parliament, citing the West’s failures in Iraq, voted to reject an attack on Syria for now, because a majority did not judge the available evidence of Assad’s guilt to be definitive.

Last year, President Obama said that he would consider the use of chemical arms during Syria’s civil war a “red line” that, if crossed, would require American action. Last week, the President and his Secretary of State, John Kerry, sounded as though they had decided to strike against Assad. The dilemma they confront is a mercifully rare one. Since the First World War, there have been fewer than a dozen wars or acts of terrorism involving chemical arms. Before Syria, the last such attack occurred in 1995, when Aum Shinrikyo, a millenarian cult, released sarin gas into Tokyo’s subway because its leaders believed that mass killing would catalyze the apocalypse.

It is hard to grasp why any rational person would use chemical weapons, even amid the terrible exigencies of war. Gas weapons cannot be aimed in order to spare children or other noncombatants. They cause fear and prolonged suffering in victims, and cripple some survivors. They can contaminate the environment with poisons that last beyond a war’s end. And, because gases travel unpredictably on the wind, the weapons’ utility on a battlefield is limited.

Yet Saddam saw great value in chemical arms during the nineteen-eighties, and his twisted logic bears examination in the light of Syria’s deteriorating conflict. Saddam first used gas bombs to thwart Iran’s zealous swarms of “human wave” infantry. Chemical terror broke the will of young Iranian volunteers, a lesson that informed Majid’s subsequent Kurdish campaign. The Reagan Administration’s decision to tolerate Saddam’s depravities proved to be a colossal moral failure and strategic mistake; it encouraged Saddam’s aggression and internal repression, and it allowed Iraq to demonstrate to future dictators the tactical value of chemical warfare.

The consequences of similar passivity in Syria now are unknowable. After more than two years and a hundred thousand deaths, the war has descended into a miasma of kidnappings, executions, and indiscriminate attacks. It would not be surprising if Assad or his henchmen seized upon selective gassings as a way to break the opposition’s will, or to flush rebels from strategic neighborhoods. Obama has said that his aim in Syria is to prevent more gassings, not to overthrow Assad. Since the costs of even a limited Western military intervention in Syria might be very high, in diplomatic standing and in lives, it is reasonable to ask whether the cause of punishing and deterring the use of chemical weapons is worth the risks.

Assad’s forces have already killed tens of thousands of civilians with conventional weaponry. But chemical warfare is a step beyond. Since the Second World War, governments and armies have gradually forsworn weapons that do not distinguish between soldiers and civilians. These include nuclear, biological, and chemical arms, and also land mines and cluster munitions. The treaties that ban such arms are building blocks in a decades-long campaign by human-rights activists to insist that warfare be subordinated to international law, that soldiers attack only other soldiers, and that generals be held accountable for where they aim their weapons.

International laws and informal warnings of retaliation are designed to dissuade dictators and terrorists from using weapons of mass destruction under any circumstances. A failure to enforce such norms in Syria would likely lower the threshold for chemical use in this and future wars. Obama’s deliberateness about military action in Syria is understandable. The consequences of intervention may be difficult to control; the Syrian opposition is fractured and influenced by jihadi fighters. As Iraq has shown, the public requires transparency, accountability, and democratic deliberation when war crimes become a basis for more war.

In Iraq, starting in 2006, Chemical Ali went on trial for mass murder and other crimes against humanity. The proceedings were undeniably flawed. Yet they put Majid’s murderous arrogance on full display to his countrymen, and guaranteed that the record of his guilt can never be obscured. He was hanged in 2010. The prospect of even such rough justice for Syria’s chemical bombers looks elusive. Yet Obama’s original instincts were sound. There are red lines even in a war as devoid of clarity as Syria’s. The best available evidence is that on August 21st Bashar al-Assad’s forces crossed to the other side. ♦