Military responses to problems have a way of creating all sorts of new problems. The tenth anniversary of the 9/11 tragedy offers an opportunity to reflect on the costs and benefits of the wars the United States initiated against Iraq and Afghanistan after the terrorist attacks. A comprehensive new study, “Costs of War,” sponsored by Brown University (and with which I have been affiliated) suggests that the costs have been wildly out of proportion to the benefits.

Military responses to problems have a way of creating all sorts of new problems. The tenth anniversary of the 9/11 tragedy offers an opportunity to reflect on the costs and benefits of the wars the United States initiated against Iraq and Afghanistan after the terrorist attacks. A comprehensive new study, “Costs of War,” sponsored by Brown University (and with which I have been affiliated) suggests that the costs have been wildly out of proportion to the benefits. The study should be required reading for political commentators and national security policymakers across the country. Presidential speechwriters’ inspiring words about the courage of American soldiers and the success of the “surge” notwithstanding, it is hard to find any metric by which one can judge the wars in Iraq and Afghanistan as successes. In money and in human suffering, the expense of the wars has been appalling — as the Costs of War website makes clear, with a mixture of snappy graphics and carefully sourced research.

We could pull every last soldier out of Iraq and Afghanistan tomorrow, but the costs of caring for them will keep climbing until at least 2040.

The most obvious damage has been financial. Of all the nation’s wars, only World War II cost the United States more than the wars in Iraq and Afghanistan. Although leading neoconservatives from Paul Wolfowitz to Ken Pollack predicted that the war in Iraq would largely pay for itself, the Nobel Prize-winning economist Joseph Stiglitz and his collaborator Linda Bilmes estimate that, in funds already disbursed or committed, the wars in Iraq and Afghanistan have so far cost the American taxpayer a whopping $3.2 trillion — at least.

Given the current preoccupation with the deficit in Washington, it is noteworthy that this $3.2 trillion includes $200 billion in interest payments incurred on these wars since 2001. That’s because the Bush administration decided to pay for these wars by borrowing rather than by taxing the people on whose behalf the wars were fought. If Congressional Budget Office predictions are borne out, the United States will spend another $800 billion in war interest by 2020.

This hemorrhaging of money has collateral effects on the US economy. All that government borrowing makes it harder for consumers to borrow money, pushing payments on the average American’s mortgage up by $600 a year, for example. The wars have also driven up the price of oil, thus magnifying the recession, and they have siphoned off over $3 trillion that could have been invested in the renewal of US infrastructure. Or in jobs: $1 million spent on the military creates 8.3 jobs, whereas $1 million spent on education creates 15.5 jobs and $1 million spent on health care creates 14.3 jobs. If we estimate that the Pentagon spent $130 billion a year directly on the wars, that money, if spent at home instead, would have created 900,000 US jobs in education or 780,000 US jobs in health care.

And then there are the dead, the injured, and the displaced. So as to avoid charges of sensationalism, the Costs of War project deliberately uses conservative numbers where estimates differ, but even the conservative numbers are horrifying. While some studies put the numbers of Iraqi dead higher than one million, the Costs of War project goes with the lower number of 225,000 individual Afghans and Iraqis who are known to have lost their lives; 137,000 of these were civilians. Almost eight million Iraqis and Afghans — a number as large as the combined populations of Connecticut and Kentucky — are thought to be displaced. At 6,000, the number of American troops killed is much smaller, but it is still more than twice the number lost in the terrorist attacks that so traumatized the country a decade ago. And each dead soldier leaves behind a hole in someone’s heart.

If the newspapers periodically remind us of these slain American soldiers by showing us the “faces of the fallen,” the injured are less visible, but the cost of caring for them will only increase. Nearly 100,000 American soldiers have been officially wounded in Iraq and Afghanistan, but many injuries, such as post-traumatic-stress disorder, may not manifest until after deployment. More than 522,000 veterans of our Middle Eastern wars have now filed disability claims. Based on prior experience in World War II, Korea, and Vietnam, we know that the health care costs of such veterans do not peak until 30 to 40 years after the wars are over. In other words, we could pull every last soldier out of Iraq and Afghanistan tomorrow, but the costs of caring for them will keep climbing until at least 2040. These costs are expected to total between $600 billion and $1 trillion.

Of course, some of these veterans will pay the costs of war in other ways: The military suicide rate is twice the civilian suicide rate, and veterans are 75 percent more likely than civilians to die in car crashes. An ongoing US government survey has found that over a quarter of veterans of the Iraq war are abusing alcohol, and the rate of abuse of prescription drugs by military veterans is now six times greater than it was in 2002.

Meanwhile, two million American children have lived in recent years with the stress of a parent deployed to Iraq and Afghanistan. Some have seen parents return from war with amputated limbs, brain injuries, and post-traumatic-stress disorder. These children, disproportionately from minority communities, are more likely than their civilian counterparts to have problems at school, to suffer from depression, and to exhibit behavioral disorders. They represent another kind of interest on our investment in war — one that we will be paying back for a long time. As we pare back social services as part of federal budget cuts, many of these children and their families will struggle with their problems on their own — an intolerable externalization of the costs of war for a society that claims to be committed to family values.

When we hear our leaders talk about “military operations” and “surgical strikes,” it is tempting to think of military force as a powerful but precise tool for achieving objectives like the removal of Saddam Hussein or the defeat of the Taliban. We have learned from Iraq and Afghanistan (having apparently forgotten the earlier lesson administered by the Vietnamese) that the tools of war cost a lot to wield, that they end up killing many innocent people as well as their intended targets, and that the blowback from war leaves a trail of devastated and diminished human beings who struggle with the consequences of war for decades after the last soldiers have laid down their weapons.

As Dana Priest and William Arkin say in their fine new book, Top Secret America, Americans “have shelled out billions of dollars to turn the machine of government over to defeating terrorism without ever really questioning what they were getting for their money.” The tenth anniversary of 9/11 is a moment for reflection, yes, but it is also an opportunity to start asking some hard questions.