Captain Alfred F. B. Carpenter A Portion of the German Battery on the Lighthouse Extension of the Mole View of the Canal Entrance with its Curved Piers Aerial Photograph of the Canal Entrance The Northeastern End of the Mole The Blockships fitting out for the Enterprise H.M.S. Vindictive before Fitting Out A Portion of the Broad Part of the Mole The Outer Wall, Showing the Parapet Pathway Sixteen Feet Above The Floor of the Mole H.M.S. Vindictive's Specially Constructed Gang-Ways One of the Monitors H.M. Ships Iris (right) and Daffodil Lieut.-Col. Bertram N. Elliot Lieut.-Commander Arthur L. Harrison Wing-Commander Frank A. Brock Captain Henry C. Halahan Vice-Admiral Sir Roger J. B. Keyes (missing from book) Diagrammatic Sketch of the Attack Drawn By Charles De Lacy From Details Supplied By The Author H.M.S. Vindictive's Bridge and Flame-Thrower Hut (right) {xxiv} The Fight on the Mole Drawn by Charles De Lacy from details supplied by the author Lieut. George N. Bradford Lieut. Claude E. K. Hawkings Lieut. Richard D. Sandford Commander Valentine F. Gibbs The Railway Viaduct Aerial Photograph taken through the Clouds a Few Hours after the Enterprise The Three Blockships shortly after the Attack Intrepid and Iphigenia The Western Side of the Blocked Channel The Eastern Side of the Blocked Channel H.M.S. _Vindictive_ at Dover after the Attack H.M.S. _Vindictive_ on her Return to Dover MAPS AND PLANS Chart showing the Relative Positions of Dover, Zeebrugge, Heligoland, and the Exits from the North Sea The Canal System of Belgium The Port of Zeebrugge Chart of Dover to Zeebrugge Plan of Canal Entrance Channel Sectional Sketch of Sunken Blockships Section of the Mole through No. 3 Shed Specimen Diagram for ascertaining Available Period {1} THE BLOCKING OF ZEEBRUGGE PART I {3} THE BLOCKING OF ZEEBRUGGE CHAPTER I THE STRATEGICAL SITUATION. THE GERMAN BASES IN FLANDERS. THE CONCEPTION OF THE PLAN. The main function of a navy in war is that of obtaining the command of the sea. The purpose for which such "command" is desired is the utilisation of the sea-lines of communication and the denial of the same to the enemy. Soon after the commencement of the war in 1914 the sea-lines of communication across the English Channel assumed considerable, if not paramount, importance for the transfer of personnel and material from Britain to the Allied forces in France. It was equally incumbent on the navy to maintain the trans-Atlantic and other lines of communication along which the necessities of life and war were carried to the Allies in all theatres of war. [Sidenote: The Strategical Situation]