The factors which combined to make "the game worth the candle" were as follows: firstly, the use of smoke screens; secondly, the element of surprise and the use of diversionary measures; thirdly, detailed preparation and determination combined with efficiency. The use of smoke screens provided a factor which had been absent in previous attempts in history. Mention has already been made of the great deterrent afforded by the presence of hostile batteries and of the varying degrees of efficiency of gun-fire as a defence against attacks from the sea. If smoke could be utilised in such a manner as to hide the attacking force from the batteries without completely blinding the former, and if at the same time the attack could be made under cover of darkness so as to prevent aircraft from assisting those batteries, a set of conditions less unfavourable to the attackers would then be forthcoming. Obviously, this necessitated the smoke drifting shorewards ahead of the approaching vessels; i.e., the assistance of a wind blowing more or less directly towards the shore. It is well here to caution the reader against a commonly erroneous idea in this connection. It is often supposed that the use of smoke was a sort of panacea for all evils, that it provided a counter to all obstacles. This was very far from being the case, as will now be {60} explained. Firstly, let us consider the navigational difficulties. Smoke could not possibly assist the ships to avoid shoals when approaching the coast. Smoke could not prevent the vessels from being seen and reported by surface patrol craft, submarines, or aircraft during the trip across the sea. The danger from mines could not be avoided by the use of smoke. It has already been pointed out that it is quite difficult enough to locate one's destination on a dark night when the lighthouses have been extinguished and other navigational aids withdrawn. Even a landsman will realise that if, as an addition to such inconvenient conditions, one places an artificial fog between the approaching vessels and their destination the problem is not going to become any more easy to solve. The utmost that one could gain from the use of smoke was some measure of protection from the shore batteries, but, as just shown, such use provided a further obstacle to be surmounted. Then again there is nothing so fickle in the life of a sailor as the wind. If the wind died away or changed to an off-shore direction, smoke might be practically useless for covering one's approach. I have sometimes been asked why we made no use of poison gas clouds. There were two main reasons. The last thing we desired was to risk killing those downtrodden Belgians who were still allowed to reside in their unhappy country. In addition to that, the fickleness of the wind might waft the poison gas in the direction of our own vessels. [Sidenote: Surprise Essential]