In a letter to a British parliamentarian last month, a senior State Department official insisted that the United States was “doing its utmost” to ensure that Iraq’s government would treat 3,400 Iranian exiles living at Camp Ashraf in eastern Iraq “humanely.” Two weeks later, a clash between the exiles and Iraqi police left 11 Iranians dead, and 36 were taken into custody by Iraqi forces. Americans troops had guarded the camp since 2003, but recently handed over responsibility to Iraqi forces. Baghdad promised that the exiles would be protected. There is no authoritative version of events, but it does not...