WASHINGTON (AP) — A House Republican chairman is doggedly pursuing the question of whether military personnel were told to “stand down” during the 2012 deadly assault on the U.S. diplomatic mission in Benghazi, Libya, despite the insistence of military leaders and other Republicans that it never happened.

Rep. Darrell Issa’s Oversight and Government Reform Committee is pressing officials in a series of closed-door meetings about the instructions from military commanders in the chaotic hours after the first attack and whether they were told not to assist Americans under siege.