If you concur with these conclusions, what principle will govern your action in putting the farm into a state of defence? You will notice that the farm shows a bigger front to the east and the west than it does to the north and the south. It is constructed of strong masonry and has two stories. _Action which is considered Correct._ You should use the southern rooms in the farm for your machine guns rather than the northern ones, as you will there be more protected from shell fire. You must keep your defence as much below ground as possible, using cellars if they are available, and otherwise digging trenches inside the walls so as to have your loopholes a few inches above the ground level. Construct head cover with strong baulks close over your heads, so that in the event of the whole building being brought down, it will not affect you, but only give you more cover from high-angle fire. If possible put wire round the northern end of the building. Arrange to flank the work between _M N_, which should in turn protect your front. [Illustration: _Work for 40 men & 2 m. gs. or Lewis guns. It only requires 40 to hold it, but would give cover to twice as many_ _Angles at B & C arbitrary to suit ground._] _Question 3._ What description of work will you make between _M_ and _N_? _Action considered Correct._ The best form of work to construct will be one made on the principle of that shown in the annexed diagram. As will be seen, this consists of a series of island traverses strung together more or less in the shape of an “S.” The advantage of this is not only that it is suitable for all-round defence, but that the whole of the garrison can fire simultaneously in almost any direction, the weakest points being _A_ and _D_. The work shown in the diagram would require a garrison of about forty men, but it could give cover to eighty. It is less vulnerable by artillery fire than almost any other form of work. It is an easy work to construct in so far that a large number of men can work at it at the same time without interfering with each other. The acuteness or obtuseness of the angles at _B_ and _C_ must depend entirely upon the ground, but it stands to reason that the more the angles approach right angles, the more is the work suitable for all-round defence. The “crucifix” strong point is also a good pattern, but I think that the one that I have given you is better, as it is in every way a less satisfactory mark for the enemy artillery, and also gives you quite as good, if not better, opportunity of using all your rifles in every direction. My next letter will contain a problem for a rearguard commander. Your affectionate father, “X. Y. Z.” LETTER V [Illustration] _January 1, 1918._ MY DEAR DICK,--