OFFICIAL HISTORY OF THE GREAT WAR. Full 3 volume set SEABORNE TRADE.

Volume I. The Cruiser Period covers from
the outbreak of the War in 1914 through to about February 1915. It chronicles the operations of German surface raiders and submarines in European waters, the North and South Atlantic, the Mediterranean and the Pacific. There is a heavy emphasis on naval operations and how they affected merchant ships.

.VOLUME II; SUBMARINE CAMPAIGN (FROM THE OPENING OF THE CAMPAIGN TO THE APPOINTMENT OF A SHIPPING CONTROLLER)covers the early period of the German submarine campaign from Feb. 1915 to Dec. 1916. It covers the impact of increased German submarine operations, the higher demands made for food and material, not only in the United Kingdom, but for France and the Allies and in support of overseas operations.

VOLUME III: THE PERIOD OF UNRESTRICTED SUBMARINE WARFARE
this final volume covers the period from January 1917 to the end of the war in November 1918, a period which saw the onslaught of unrestricted submarine warfare by the Imperial German Navy.