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Each turn you have to search for a target, check out what kind of protective escort it has and decide on a method of attack. Each stage is a decision and committing to the wrong sort of target means you might risk being sunk or worse yet, returning home with a trivial tonnage of sunk enemy shipping.
The game is Print and Play, meaning you download a file and print out the game components yourself. It's been deliberately created in black and white with a minimum of expensive ink usage. It plays in about 10-20 minutes and makes a nice filler.
Buy the game online at Wargame Vault