Historical clue formulations

• Enemy W.W. II vessel — 2025-12-17
• W.W. II menace — 2025-10-07
• German war vessel — 2025-07-10
• Menace in "Dead Wake: The Last Crossing of the Lusitania" — 2024-10-26
• German sub in W.W. II fighting — 2024-04-29
• W.W. II sub — 2023-07-06
• Threat to the Allies in W.W. II — 2022-02-02
• W.W. II threat — 2021-09-26
• In-depth subject for a war historian? — 2021-05-01
• Wolf pack vessel in W.W. II — 2020-08-11
• W.W. II German sub — 2020-02-24
• Something forbidden by the Treaty of Versailles after W.W. I — 2020-01-17
• Menace in the 1957 film "The Enemy Below" — 2018-10-17
• W.W. II menace — 2018-02-28
• W.W. II danger — 2017-06-04
• W.W. II danger — 2016-12-11
• W.W. II German vessel — 2016-06-13
• See 23-Across — 2016-04-10
• Destroyer destroyer — 2015-12-29
• Lusitania sinker — 2015-07-14
• Source of doom for the 17-Across — 2015-06-26
• Battle of the Atlantic craft — 2015-02-13
• See 7-Down — 2014-04-10
• Raider in the battle of the St. Lawrence — 2014-01-04
• W.W. II menace — 2014-01-01
• Wolf pack member — 2011-09-10
• W.W. II ship sinker — 2011-07-18
• Battle of the Atlantic vessel — 2011-04-17
• W.W. II blockade enforcer — 2010-04-29
• Maritime threat of the early 1940s — 2010-03-28
• W.W. II sea menace — 2010-01-05
• W.W. II German sub — 2009-08-24
• W.W. II menace — 2009-07-22
• Torpedo launcher — 2009-05-26
• German diver — 2009-03-20
• W.W. II Atlantic lurker — 2009-02-23
• W.W. II blockade enforcer — 2008-09-25
• Ship sinker — 2008-08-01
• Liner threat, once — 2008-01-26
• Kriegsmarine vessel — 2007-09-18
• Naval convoy menace — 2007-04-24
• W.W. II menace — 2006-01-08
• Q-ship's quarry — 2005-05-15
• Wolf pack member — 2005-03-23
• Lusitania sinker — 2004-12-26
• One in search of a tin can — 2004-09-09
• W.W. II vessel — 2004-03-29
• W.W. II predator — 2004-03-26
• The Lusitania's undoer — 2003-09-09
• W.W. II danger — 2003-04-16