A YEAR AGO, possible civilian casualties loomed large in the debate over whether to invade Iraq. Opponents of the war estimated likely casualties in the hundreds of thousands. One heavily cited United Nations report projected 100,000 to 500,000 Iraqi civilians would die or suffer injury and/or starvation. Of course, those projections were wildly off. Just after Baghdad fell, University of Chicago political scientist Daniel Drezner pointed out that casualties had been "less than one percent of what was projected." But everyone agreed that estimates of civilian casualties deserved to be factored into our decision.

Today's debate would benefit from a second estimate. How many Iraqi civilian lives have been saved by the use of force against Saddam? John Burns, who covered the war for the New York Times, guessed that in the first six weeks of war fewer Iraqis had died than would have "if Saddam Hussein's killing machine had gone about its daily business." Estimating how many lives have been saved by a tyrant's overthrow is as messy and hypothetical as projecting how many will be lost in a coming war, but the exercise is based on something concrete. Saddam's regime murdered people every year, and would have murdered some number of people had it remained in place over the past 12 months. We can't know exactly how many. But we can make an educated guess based on the regime's record--its long-term rate of killing--combined with its behavior in the period leading up to its overthrow.

Figuring out exactly how many people were killed in Saddam's 24 years as president of Iraq isn't easy. Saddam's murders were frequent and numerous, but the victims and their executioners were often the only witnesses. The true extent of his murderousness will be revealed only when Iraq's many mass graves are exhumed, an enormous and painfully slow task that has just begun. For now, though, we have credible estimates to work with. Almost certainly, most of them understate the regime's bloodletting.

In 1979, when Saddam became president, violence in Iraq escalated dramatically. The regime committed both individual murders and mass murder. The former category eliminated individuals suspected of anti-regime (or just anti-Saddam) sentiments or activities. This included Saddam's personal and factional enemies in the party, disloyal (or insufficiently obsequious) military officers, active or suspected dissidents in Iraq's general population, and many others whose only sin was being a friend or relative of such persons. In 1989, Amnesty International reported hundreds of such executions per year, stretching back over a decade. Some years, these murders reached into the thousands. Of course, any numbers derived from these killings do not include many thousands of cases of torture, rape, amputation, branding, and other atrocities committed by Saddam's regime that stopped short of death.

Its rate of killing was far higher when the regime targeted entire communities. Shia Muslims, ethnic Kurds, and smaller ethnic and religious minorities were constantly subject to violence from the regime (as well as many other forms of repression). In his first dozen years in power, Saddam assaulted at least one of these groups with truly massive violence on average every three years. After Iran's Shia revolution, Saddam became concerned that Iraq's own Shias might try to follow suit. In 1980, Iraq attacked Iran, at which point Saddam wanted also to ensure that Iraqi Shias would not assist their Shia brethren. To these ends, the regime murdered thousands--quite possibly 50,000, according to Human Rights Watch--including Shia clerics.

The Iran-Iraq war put large strains on Iraq's economy, military, and regime. Saddam dealt with the resulting problems in characteristic fashion. Just as with Stalin during World War II, large amounts of blood were shed not only on the military front, but also behind it. Shias were not the only targets. In a single episode in the mid-1980s, the regime rounded up and killed around 10,000 Kurds. Even before the war ended, the regime launched a much more ambitious program to wipe out entire Kurdish communities. It was in this military campaign--named Operation Anfal--that the regime used chemical weapons against several Kurdish towns, killing thousands. Human Rights Watch estimated that Anfal killed "more than 100,000" Kurds, and that Kurdish victims of the regime's campaigns between 1983 and 1993 reached "well into six figures."

Kurdish groups estimate Anfal's victims were even higher, up to 180,000. Whatever the exact number, Human Rights Watch concluded that "the Iraqi regime committed the crime of genocide." Anfal's intense phase lasted three months in the spring of 1988. If we estimate its victims at 100,000, the regime was killing Kurds alone at a rate of around 30,000 each month, or a thousand a day.

The collapse of most of Saddam's army in the first Gulf War inspired an uprising or intifada within the military and among the Kurds and Shia. The regime responded with the largest killing spree in its history.

Unfortunately, little information is available about the violence directed against Shias, who are believed to have suffered the worst of this backlash. Initial reports conservatively estimated at least 50,000 Shia victims. More horrifying--but believable--reports have come from Iraqi state security officials who fled Saddam's fickle wrath after 1991. One defecting officer reported that he supervised the killing and burial of approximately 4,000 Shias at one site in one morning alone--this, in an operation that lasted weeks. The U.S. report "Life Under Saddam Hussein" states that "Iraqi officials themselves have privately acknowledged that the regime slaughtered as many as 200,000 Shia" or even more in 1991.

The number of Kurds who died in 1991--killed by Saddam's forces or fleeing them--is estimated at 50,000 to 80,000. This range would have been much higher, except that the Gulf War Allies intervened in Iraq's north in response to the massive flow of desperate Kurdish refugees escaping the regime's onslaught. While it was allowed to proceed, the regime killed Kurds at a rate of tens of thousands a month. The regime also killed an unknown number of people living in Iraq's southern marshes in military campaigns stretching into 1992.

This means that for a time in the early spring of 1991, Saddam's regime was killing Shias and Kurds combined at a rate of tens of thousands per week, and would have gone on doing so in the north for much longer had the Americans, British, and French not created a "safe haven" for Kurds inside northern Iraq, which Saddam's forces were basically barred from entering.

In the 1990s, Saddam's regime continued to commit individual political murder. Victims included people suspected of anti-Saddam activity, others who were friends and relatives of the suspected subversives, as well as people caught up in the mafia-like violence of Uday Hussein and other regime figures. Throughout these years, Amnesty International catalogued credible reports of hundreds of killings every year, and quite possibly thousands in several years.

From 1997 to 1999, the regime "cleansed" its prisons, executing up to 2,500 people. Around the same time, the regime began a new campaign against selected Shia. Prominent Shia clerics were assassinated, prompting public demonstrations, which were savagely suppressed with an unknown number of victims. And a new military offensive was launched against groups in the southern marshes in 1998. In the decade leading up to the Coalition invasion, political murder also extended deeper into the regime's ranks than ever before. Thousands in the military died in periodic purges, and killing extended even into Sunni tribes and Saddam's own family.

Four months before Saddam's fall, Human Rights Watch estimated that up to 290,000 people had "disappeared" since the late 1970s and were presumed dead. The Coalition Provisional Authority's human rights office estimates that 300,000 bodies are contained in the numerous mass graves. "And that's the lower end of the estimates," said one CPA spokesperson. In fact, the accumulated credible reports make the likely number at least 400,000 to 450,000. So, by a conservative estimate, the regime was killing civilians at an average rate of at least 16,000 a year between 1979 and March 2003.

HAD SADDAM REMAINED IN POWER over the past year, individual political murders would have continued, and might well have accelerated given the tensions and fears caused by his regime's high-wire confrontation with the Coalition countries. This would have meant several thousand deaths. What of murders committed en masse? Between 1991 and March 2003, the regime carried out no exterminations on the scale of Anfal. Had the leopard changed its spots? Hardly. The few years leading up to the invasion suggest events might well have been building to another round of mass murder. Some totalitarian regimes kill so many of their opponents and smash civil society so completely that eventually no group has the resources to threaten the regime in any way. This explains why the Soviet Union killed fewer people after Stalin. Saddam's regime never achieved this goal. To the very end, Iraq contained large groups that Saddam was prepared to target with massive violence.

How many Iraqis were saved by the use of force against Saddam can be counted in several ways. At a bare minimum, several thousand Iraqis were saved from being killed in individual political murders. This includes political prisoners (including children) who poured from Saddam's dungeons at liberation, Shia activists, other dissenters, and military men suspected of disloyalty. Toppling Saddam also saved several thousand more at dire risk from his gradually rising violence against the Shia. If the Shia or Kurds were targeted with wholesale murder, as seemed increasingly likely, the regime could easily have resumed killing at its historic rate of 15,000 to 20,000 deaths a year. Specifically, the West's already existing threat to use force inside Iraq to protect Kurdistan--a threat whose credibility might well have collapsed if the Coalition had crumbled last year--saved tens of thousands more from certain death every year it was in place.

U.N. economic sanctions were also killing civilians. Critics regularly claimed sanctions caused 4,000 to 5,000 Iraqi children to die per month from poor nutrition and health care. UNICEF attributed some 500,000 unnecessary deaths to the sanctions in the 1990s. The sanctions remained in place as long as Saddam's regime refused to comply with international requirements. Liberation made it possible to lift the sanctions almost immediately--thus saving approximately 60,000 lives a year, if we use UNICEF's numbers.

At some point in the past year, the number of Iraqi civilians who would have been killed by Saddam's continuing rule surpassed the number who died because of the war. We will never know for sure when that moment occurred, whether earlier or later than the six-week mark guessed at by the New York Times's John Burns. But it has long since passed. And that margin will grow with each passing year that Iraqis are free from Saddam. People genuinely motivated by a concern for Iraqi civilians have much to be grateful for. Terrorist bombings inside Iraq since liberation show just how little Baathists value Iraqi civilian lives, and just how ready they would be to resume mass murder if the world let them.

Gerard Alexander is an associate professor of politics at the University of Virginia, where he teaches a course on the politics of the Holocaust.

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