Serpent of mud

From ‘The fall of Combles and Thiepval’, The Spectator, 30 September 1916: The trench — ugly, dirty, dull, untidy serpent of mud and sandbags — will always have the advantage of the most artful fortress. In the last resort, the reason for this seeming miracle is the fact that the trench has something of mobility in it, and mobility is the vital essence of war. You can prolong a trench line to infinity, or to the sea or a neutral frontier, which is even better than infinity. A fortress has a finality about it which is fatal. The moment mobility is abandoned, as in an invested fortress, putrefaction, physical and spiritual, seems to set in.