Germany’s very existence depended upon the import of iron ore from Sweden. For the first war year the Germans were counting on eleven million tons of it out of a total annual consumption of fifteen million tons. During the warm-weather months this ore was transported from northern Sweden down the Gulf of Bothnia and across the Baltic to Germany, and presented no problem even in wartime, since the Baltic was effectively barred to British submarines and surface ships. But in the wintertime this shipping lane could not be used because of thick ice. During the cold months the Swedish ore had to be
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