Cause of death: Washington faltered as fentanyl gripped America

During the past seven years, as soaring quantities of fentanyl flooded into the United States, strategic blunders and cascading mistakes by successive U.S. administrations allowed the most lethal drug crisis in American history to become significantly worse, a Washington Post investigation has found.

Presidents from both parties failed to take effective action in the face of one of the most urgent threats to the nation’s security, one that claims more lives each year than car accidents, suicides or gun violence. Fentanyl is now the leading cause of death for Americans ages 18 to...