WASHINGTON — Top national security officials trudged to Capitol Hill Thursday to grapple with fallout from the David Petraeus sex scandal as Defense Secretary Leon Panetta asked service chiefs to review ethics training for military officers. He said he was unaware of any other top brass who could turn out to be ensnared in the debacle.

One person missing from the tableau: General John Allen, the commander of coalition forces in Afghanistan whose nomination to take over in Europe is on hold because of suggestive e-mails turned up in the investigation.