For two years, the historian had been visiting a National Archives facility in Maryland to review files on U.S. pilots who had crashed in German-controlled Europe during World War II.

Last week, Antonin Dehays, a 32-year-old Frenchman, finally acknowledged one reason why, federal investigators say: He’d been stealing the dog tags of dead American heroes, selling many of them on eBay.

“The theft of our history should anger any citizen,” the Archivist of the United States David Ferriero said Tuesday in a statement, “but as a veteran I am shocked at allegations that a historian would show such disregard for records and artifacts documenting those captured or killed in World War II.”

If convicted, prosecutors say, Dehays could face up to a decade in prison. In 2005, a Virginia man was sentenced to two years for stealing dozens of Civil War-era documents, including letters by Jefferson Davis and Robert E. Lee, from the National Archives. And five years ago, an Archives official admitted to stealing nearly 1,000 recordings, many of them rare. ...