After hard fighting you have driven the enemy out of the trench _A B C_, and he has retired up the communication trench _D E F_ in the direction of his supports. You are in command of a platoon and have been ordered to take steps to prevent the enemy again advancing along the communication trench _E D B_. It is not the intention of your commanding officer to advance at present any farther than the points he has already reached. The time is an hour before dark. What steps will you take to carry out the instructions you have received? _Solution considered Correct._ Pull knife-rests[2] down into the trench _D E F_, also throw wire into it if available. At once put a couple of men at the point _D_ to cover the trench _D E_ with their rifles. As soon as you are able to do so, dig a short trench from _G_ to _D_ and place a Lewis gun at _G_ to enfilade _D E_. You may have to wait until after dark before you actually carry this out, but you should make arrangements for doing it by daylight. It would not be a bad plan to tie a few tins on to the knife-rests which you have thrown into the trench, so that the rattle, if they are moved, will give you warning of any one’s approach. The Lewis gun at _G_ will be practically out of bombing range from _E F_. [2] A knife-rest is a portable wire entanglement about 10 feet long, made upon a wooden frame-work. [Illustration] * * * * * There are as many different types of stops as there are different sorts of trenches. Some of these types are better than others, but there is no type which is suitable under all circumstances. Everything must depend on the exact local conditions and on the means at your disposal. It does not require much ingenuity to devise a good stop for a trench if you have leisure to think the matter out, but just as a remark which would be commonplace if given as the result of matured deliberation is regarded as brilliant if made as a quick repartee, so in tactics to do what is right under fire is quite a different thing to answering a question on an examination paper. Nevertheless, to have answered a similar question on an examination paper, or, still better, to have done it as a tactical exercise, renders it very much more likely that you will do the right thing when you are faced by a similar problem in earnest. I, therefore, counsel you to carefully consider the different sorts of trenches which you come across and to think out carefully how you would put a stop in them, or how you turn them to shoot in the opposite direction. In the diagram I have given you it is just possible that by cutting down the elbow at _E_, you may be able to enfilade the section of trench _E F_ from _A_. This would, however, depend on the ground and on the actual construction of the trenches concerned. Your affectionate father, “X. Y. Z.” LETTER IX [Illustration] _February 1, 1918._ PROBLEM 9 MY DEAR DICK,--