At high tide the tidal current on the Belgian coast is flowing at its greatest speed--a phenomenon nearly always found in comparatively narrow waters--and its rate was expected to be about three and a half miles per hour, its direction of flow being to the eastward. So far, then, the matter of reaching a position alongside chiefly concerned the art of seamanship if we leave the enemy's opposition out of account. Next we had to consider the problem of securing alongside and of disembarking the storming parties. The most simple method of berthing alongside a wall, in the case of a sizable vessel, is to place the vessel roughly in position and then to use tugs to push her bodily against the wall, afterwards securing the {76} hawsers in the usual manner. This led to the idea of having a second vessel to act as tug and of providing special means to take the place of the ordinary hawser-and-bollard method of securing. The wall on the outer side, as previously described, rose to a height of twenty-nine feet above the level of high water. This height was far above that of the deck of an average vessel. The fact that the landing would have to be made on a narrow parapet, high above the level of the Mole proper, was also hardly calculated to assist matters. The probable existence of guns on the parapet itself, so placed as to be able to rake the decks of a vessel alongside, and the possible presence of obstructions placed by the Germans on the outer side of the Mole, had to be taken into account. It has also been mentioned above that the use of smoke screens necessitated a wind blowing towards the shore; thus the Mole itself could afford no protection from the wind or sea. The Austrian military failure on the River Piave, during the late war, afforded a good example of the disabilities resulting from insufficient room to debouch a force which has crossed an obstacle into the enemy's territory. Clearly, it might be very awkward if the storming parties were unable to descend from the parapet rapidly enough to forestall any enemy attempts at concentration near the storming point. All these considerations led to the choice of H.M.S. _Vindictive_ for carrying the main portion of the storming parties. The attack on the Mole might also provide an opportunity for destroying material thereon. Although this was obviously a secondary consideration it was {77} an opportunity not to be missed. The amount of destructive work which could be done would depend upon the circumstances of the moment, but it was decided to have a special demolition party, provided with the necessary gear, to accompany the primary attacking forces. [Illustration: THE OUTER WALL, SHOWING THE PARAPET PATHWAY 16 FEET ABOVE THE FLOOR OF THE MOLE]