What did the Red Navy do during the war?

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The Eastern Front in Europe was primarily a land based war but I have wondered about what the Red Navy did during it. I am doubtful that Stalin would let it just go to waste by doing nothing but I am unaware of any major sea battles in the Baltic Sea or of U-Boats being prevalent there. So what did the sailors and ships do to help win the war? Love all of your videos and try to watch them as soon as possible after they are uploaded. Please keep up the great work.