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 and Caspian coasts. The White Sea Canal was also constructed with military use in mind, and early in its history the canal was used to transfer the Northern Fleet's first warships to the White Sea from the Baltic. According to historians, in the years between the canal's completion and the Soviet entry into World War II, the canal was used for the transfer of military vessels between the two seas on 17 occasions. During World War II, in August–September 1941, the canal was used to move a number of submarines from the Baltic Fleet to the White Sea. That included