Secretary of State John Kerry made a surprise visit to Baghdad to ask the Iraqi government to stop helping Iran support Syria's Bashar al-Assad. Kerry received an embarrassing rebuff--so much for the Bush administration's celebrated victory over Saddam Hussein. This time ten years ago the grand Iraqi cakewalk had begun. American military forces were racing toward victory. The world was going to be transformed. But not in the way President George W. Bush and his top officials imagined. Invading Iraq turned out to be one of Washington's greatest strategic mistakes. Yet even now many of the Iraq War's architects are clamoring for more wars. America needs peace. War should be a true last resort, not just another policy option for frustrated social engineers and impatient internationalists. Wars are sometimes tragically necessary. But not in Iraq.