How U.S. and Iran found a common enemy in ISIS

In a 2016 offensive to take Mosul back from ISIS, the U.S. and Iran fought on the same side without ever publicly acknowledging it. The militant group defeated, both countries still have a stake in Iraq and tensions have been rising. Special correspondent Reza Sayah has the final installment of our series Iran Rising in Iraq, in partnership with the Pulitzer Center on Crisis Reporting.