On March 20, 2003, President George W. Bush announced the U.S.-led invasion of Iraq to topple Saddam Hussein and destroyed his alleged stockpile of weapons of mass destruction.

But U.S. forces found no WMD, and rather than greeting the invaders as liberators after reaching Baghdad, Iraqis soon treated them as occupiers, leading to years of civil war that claimed hundreds of thousands of lives across the sectarian divide.

History As It Happens podcast host Martin Di Caro interviews Melvyn Leffler, a preeminent scholar of U.S. foreign policy, about why the U.S. went to war in 2003.

Mr. Leffler’s new book is “Confronting Saddam Hussein: George W. Bush and the Invasion of Iraq.”