Unseen WWII menace

This crossword clue is for the definition: Unseen WWII menace.
it’s A 18 letters crossword puzzle definition.
Next time, when searching for online help with your puzzle, try using the search term “Unseen WWII menace crossword” or “Unseen WWII menace crossword clue”. The possible answerss for Unseen WWII menace are listed below.

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Possible Answers: UBOAT.

Last seen on: Wall Street Journal Crossword – November 30 2022 – Vowel Play