Strange German victory in 1941

[asa]

In my current game as German against a human Soviet opponent I managed to take Leningrad, Moscow and Gorki. The unit occupying Gorki, however, was surrounded and the city was at SL zero from turn 22 to turn 24. In the meantime blizzards commenced and on turn 24 my opponent retook Gorki, but to our mutual surprise he got the message that Stalin was dead and Russia surrendered.
Any idea of what happened? I always thought the German would need to get all three mentioned cities with sufficient supply level in order to be awarded his full 5 points for victory...

[Mad Onion]

Mayby you captured Saratow or Stalingrad, if you did you won, if not Stalin could die in car accident and you won [:D]

[asa]

Perhaps Soviet production was too low having lost the 3 cities and maybe there is a rule in the manual that when production falls below a certain minimum amount a "sudden death" condition exists that makes the program decide that war cannot continue. Another thing is Gorki rail hex is damaged and it belongs to neither player. Gorki fell to the Germans on turn 22 and was retaken by Soviets on turn 25.