History of the North Sea the North Sea though they saw little action. The Austro-Prussian War (1866) resulted in Prussia's gaining full control of the Kiel Canal, allowing their Baltic ports access to the North Sea. France declared war on Prussia 19 July 1870 which initiated the Franco-Prussian War (1870–1871). The French Navy was, at the time far larger and superior to the North German Federal Navy, the Navy of the North German Confederation. Though the French did take a number of merchant ships bound to and from North Germany, shortages of manpower and coal, as well as conflicting orders, made the attempted blockade of
White Sea–Baltic Canal Bay near Megostrov Island; it was later captured by Finnish troops. On December 5, 1941, Finnish troops entered Medvezhyegorsk. On December 6, 1941, in a -37 °C frost, Finnish troops captured Povenets, the southern entrance to the White Sea–Baltic Canal. On the same day, Soviet troops started demolishing canal structures. Lock No. 1 was the first to be blown up. By the morning of December 8, Locks No 1 to 6, and dams No. 4 and 20 had all been demolished. At the same time heavy fighting took place in the area of the Povenets Lock Ladder (Locks No. 1