Historical clue formulations

• See 11-Down — 2026-06-03
• One can be empty or veiled — 2023-05-21
• "If you don't tell them, I will," e.g. — 2021-07-16
• Reason for an evacuation — 2010-12-29
• Security problem — 2010-12-11
• ___ level — 2009-04-18
• Declaration ending "or else!" — 2008-12-01
• It might be idle — 2007-05-10
• Terrorist tactic — 1997-01-19