A PORTION OF THE BROAD PART OF THE MOLE.
Note the concrete submarine shelter (white)
And so no method would suffice, except the second mentioned above, namely, destroying the guns or their crews, or both, or diverting their fire, by means of action on the spot. This entailed an attack on the Mole itself, carried out by vessels actually berthed alongside. The author, although well aware of the unpardonable fault of repetition, desires at this stage to lay great emphasis on the fact that an attack on the Mole itself could only be designed as a diversionary measure calculated to directly assist the blockships past one of the positions of danger. The reader is requested to pardon anticipation. Subsequent to the operation, many of the public appeared to have formed the idea that the attack on the Mole was the main attack, and that the use of the blockships was a sort of afterthought. I shall have more to say about this later.
Just as the three-gun battery provided a serious obstacle to the passage of blockships round the Mole end, so also would it prevent the similar passage of other vessels endeavouring to secure alongside the berthing wharf on the inner side of the Mole preparatory to attacking the Mole batteries. Thus, if the Mole was to be stormed, the storming parties must land on the outer side of the Mole, remembering that the three-gun battery could not fire to the northward owing to being twenty feet below the top of the high outer wall. But the outer wall of the Mole was never intended for use as a berthing position for vessels, and probably never had been used by any vessel for such a purpose—hence the complete absence of all berthing facilities as described in an earlier chapter. The development of the argument concerning this projected attack had led us to the point where we needed to consider seriously the practicability of getting any vessel, or vessels, alongside the outer wall, of securing there, and of landing men thence for attacking the Mole batteries.
The depth of water, the construction of the Mole, the rate of the tidal current, and many other matters required careful examination. The depth was a doubtful matter; but, the operation being timed to take place near high tide so that the blockships could enter the canal, there was every likelihood of its being sufficient. Breakwaters when also intended as wharfs are usually built with their inner sides—i.e., the sides protected from bad weather—vertical like the face of an ordinary wall, but with their seaward sides formed of large blocks of material dropped more or less indiscriminately, one above the other, so that the wall will be jagged for the purpose of breaking up the waves in bad weather. In such cases a ship could not possibly secure to the seaward side without being severely damaged, and certainly could not remain there. At Zeebrugge, however, we had reason to believe that the seaward side of the Mole was nearly vertical and that no danger would accrue from jagged blocks of stone or concrete.
SECTION of MOLE through No. 3 Shed
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 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.