As soon as twilight is come, aeroplanes cross the neighbouring lines and attack this tree with their machine-guns. It is treated like a combatant. Herein, perhaps, lies the secret of its clumsy strength and beauty. It stands upon its hill, solid and straight. It holds its ground as few men could do. It is a French ash that stands upon the field of battle in the very middle of the British Army. It has become an observation post. One climbs it by a straight ladder 160 feet long. In its highest fork one of the engineers has made a wooden box, bound together with barbed wire, with a little canvas to hide it. Field-glasses, maps, range-finders are there. All the gusts of the autumnal breeze blow through it. Up here, too, men are pitched about as if they were in the mizzen-top of a cruiser. Strange nest for war eagles! "Perfect weather for flying," the major tells me. A clear, frosty, moonlight night broods over the black distances of the plain. The river and its swampy edges glisten like silver coins. No sign of life. Only the guns, all round the horizon, roar beneath their crests of lightning. Imagine that after blinding yourself with a very tight and thick bandage you suddenly open your eyes. Glowing discs, will o' the wisps, haloes, flashing rainbows, a whole ballet of lights spins upon your retina. Up here, that is the spectacle that each night brings. The battlefield appears to be electrified. At one moment, sharp, stabbing flashes, cold arrows of light. It is the English guns shelling the enemy. The next, radiances which divide, spread out fanwise, or blossom like flowers. They are German marmites or crapouillots. The sounds of the guns intersect one another. They are hard and dry, when some battery, near by, opens fire; dull, soft and muffled, according as the distance becomes greater. A stroke upon a gong, followed by a long metallic shriek, high in the air, announces a heavy shell. After a hoarse scream a machine-gun begins to crackle, rending both air and men. It is all one vast intermittent hurly-burly, lightning flashing low down, V-shaped sheaves of red fire. And all is, each time, unexpected, cruelly inconsequent, magnificent and devastating. Thousands of men are there, and thousands upon thousands, all over this plain of the Ancre. There they lie, buried in their trenches, their nerves like stretched wire, ready to spring forward on the instant. From here we can see one of the last sectors to be conquered. It is land over which the offensive has passed. And our hearts ache as we remember that down there, near this swamp, it is not even in ill-made trenches that the English sections are keeping their watch, but, simply, in shell-holes, where the water lies deep, holes whose sides have been hastily shored up--veritable human hells.