Day 135 January 13, 1940

At 4.30 AM, U-20 torpedoes Swedish steamer SS Sylvia northeast of Aberdeen. Sylvia sinks within a minute with all 20 hands lost.

In a rare Soviet submarine attack, ShCh-324 surfaces and fires one torpedo (which misses) at a convoy in the Sea of Åland between Sweden and Finland. Finnish naval escort Aura II (the converted Finnish presidential yacht) drops depth charges damaging ShCh-324. However, one depth charge explodes in its thrower, obliterating the small wooden ship (26 lives lost). Finnish escort vessel Tursas picks up 15 survivors. ShCh-324 escapes back to home port.

http://users.tkk.fi/jaromaa/Navygallery/Background/Wartime/winter.htm

This is the first war in history where metal is more important than men. The ability to build and replace warships and submarines, artillery and tanks, trucks and other vehicles (rather than train and replace soldiers) is paramount. British diplomatic moves to intercept shipping in Norwegian waters threaten Swedish iron ore supplies, upon which German war production depend.