Big one. SEA MINES. Coastal and straits. Should be density level 1 - 5 and all vessels passing through have a chance of receiving damage, with vessels of the nation/allies of the nation who deployed the mines having a lower chance of damage.
As for the cities thing, it's stupid. Germany fought brilliantly in many cities - as said above. Even in Berlin, Heinrici's stand in the eastern suburbs with little but Volksgrenadiers was amazing for the last days of the Reich.
As for the cities thing, it's stupid. Germany fought brilliantly in many cities - as said above. Even in Berlin, Heinrici's stand in the eastern suburbs with little but Volksgrenadiers was amazing for the last days of the Reich.