during the first World War, they came up with the idea of 'Q' ships; they were converted freighters, with hidden cannon, etc. An unsuspecting German submarine would approach, they'd throw of the tarps, and ..whammo..
Sadly, this didn't work in WWII, the subs just sank first and asked questions after..

I wish I'd said that.. The Staircase Wit

anahl nathrak uth vas betude doth yel dyenvey..;)