Historical clue formulations

• High fortress — 2023-07-14
• Acropolis, e.g. — 2021-06-12
• The Kremlin, e.g. — 2019-07-14
• Bulwark — 2016-02-04
• Stronghold — 2013-09-29
• It may be held in battle — 2011-08-06
• The Acropolis, once — 2005-12-23
• Fortress — 2005-01-30
• Stronghold — 1999-10-24
• Stronghold — 1998-12-13
• It went coed 8/24/96, with "The" — 1998-10-29
• Charleston college, with "The" — 1993-12-04