In the second place, we had discovered that the problems of defending the Suez Canal and of defending Egypt were not identical. While the Canal formed an admirable moat, an obstacle difficult to negotiate when stoutly defended, and so a capital defensive line for the protection of the Nile; yet this line was inadequate for the protection of the Canal itself or for securing the immunity of the passing shipping. And so, thirdly, we realized that some other line must be found for the protection of the Canal. While we were sitting on the west bank, small parties of Turks approached the eastern bank. On more than one occasion, in the summer of 1915, they succeeded in placing mines in the fairway of the Canal. It would, therefore, have been quite possible for them to have seriously interfered with the working of the Canal and the passage of shipping. Granted that a new line must be found, the question arises where such new line should be drawn. A line across the actual desert may be all very well in war time, though none too easy to hold, for the reasons that we have already discussed. But to keep a garrison on such a line for ever would be well-nigh intolerable. Thus, by a process of elimination, we find that the most suitable line for the permanent defence of the Suez Canal is the fertile country beyond the eastern desert--in other words, Palestine. Fourthly, it had been brought home to us that the worst form of defence is a passive defence. As, therefore, the Turk would not leave well alone, but insisted on attacking us in Egypt, so it became necessary for us to meet him on his own ground, to push a vigorous offensive, and eventually to carry the war into Palestine. CHAPTER II THE DESERT OF SINAI In accordance with the policy of defending the Suez Canal upon a line further east, the construction of a new defensive line was put in hand during the early months of 1916. No longer were the Turks to be allowed to annoy us by actually reaching the Canal. A line of trenches, protected by barbed wire entanglements, was constructed out in the desert, a few miles to the east of the Canal. As may be imagined, this was no easy task. A large amount of excavation was necessary for a small amount of trench; walls had to be built up with sandbags; and other steps had to be taken to prevent the sides from foundering, and to construct a work that would withstand shell fire.