Tragically, the Iraq War was not worth the costs. The leading advocates for war understated the costs and exaggerated the benefits. They claimed that the war would be cheap, perhaps even profitable, thanks to lower oil prices. They suggested that it would be easy, a “cakewalk,” not requiring a long-term U.S presence to stabilize the country after Saddam Hussein’s ouster. They blithely dismissed concerns about the tensions between Arabs and Kurds, and between Sunnis and Shiites.

We now know how wrong they were. A new report from the Watson Institute for International Studies at Brown University tallies up the costs: nearly 4,500 U.S. troop fatalities, more than $1.7 trillion spent, and another $490 billion owed. Estimates of the number of Iraqis killed in the sectarian bloodletting that occurred after the collapse of Saddam’s regime exceed 130,000. Millions were displaced, many still have not returned to their homes. The Iraqi Christian community has been decimated.

The war’s benefits are few, and could have been obtained by other means. The demise of a brutal dictator is a result worth celebrating, but the imperfect and fragile government that has emerged in Iraq was hardly worth the costs incurred. As for U.S. security, war boosters declared that Saddam Hussein was actively developing nuclear weapons. Equally important, they asserted that he would use them, or give them to terrorists who would. War skeptics pointed out that this was unlikely, and they also identified crucial holes in the evidence of Saddam’s nuclear program.

War supporters hinted at possible linkages between Saddam Hussein and the 9/11 attacks; most Americans believed them. Some still do. But al-Qaida has been decimated since 2001, and the war in Iraq was, at best, irrelevant to this successful effort. If anything, the misallocation of resources to Iraq impeded the hunt for bin Laden and his cronies.

Elected officials who backed the wars have been punished at the polls. The unpopular war probably cost the Republican Party control of Congress in 2006, and Hillary Clinton’s support for the war arguably cost her the presidency. (The reputations of pundits and think tank scholars who promoted the war on faulty pretexts remain strangely intact.)

But the voices of those who warned that the war would not be worth it are now being heard. The burden of proof has shifted toward those making the case for war, in Iran, or Syria, or Yemen, or countless other places. If the country has salvaged anything constructive from this war, it seems to be a greater appreciation for war’s unpredictability and the limits of American power.