operations on both sides {81} are in the nature of a siege, and however prolonged the siege, the advantage will be gained in the long run by superiority of aggressive action in the air and over and under the ground. In addition to the absence of opportunity for the grand offensive there are two further points of difference between defensive action in Position Warfare and the defence in a War of Manoeuvre. The first of these is the inevitable absence of flanks to be assailed, as the operations necessitate a connected line of strong points from sea to sea, or from the sea to the impassable barrier of neutral territory. Mounted troops are therefore doomed to inaction in their most important sphere, until the lines have been breached and the enemy is forced to retreat, and the opportunities for delivering flank attacks are meanwhile confined to the infantry, and will be due to irregularities in the alignment of the strong points, upon which enfilade fire may be brought to bear. The second point of difference is the abundance of time at the disposal of commanders for developing and rehearsing elaborate systems of attack and defence, and for obtaining detailed plans of the hostile works, through continuous reconnaissance by the Air Service. In most countries there must be, of necessity, a prolonged period of inactivity on both sides in a Position War, owing to the severity of winter conditions, or to the occurrence of the rainy season, and during that period it will seldom be possible to penetrate the enemy's main defences on such a scale as to bring about the grand offensive. But this is a period of inactivity in appearance rather than in fact, for no defensive system is ever perfect, no strong point but needs further consolidation, new trenches are constantly constructed or improved, and fresh areas are covered with wire entanglements. Guns of all calibres, underground mines and light mortars are ever at work, demolishing, wounding, and killing, while lachrymatory and asphyxiating shell-fire is to be expected at all times. On a smaller scale, snipers on both sides have a daily bag, and {82} observers are ever at their posts noting every change, however insignificant, and every new piece of work; "listening posts" are detecting hostile plans, while patrols are collecting information and raiding parties are reconnoitring, destroying defences, and inflicting losses, it being the first principle of a raid that it should result in greater losses to the enemy than to the troops which carry it out. ENTRENCHMENTS.--Entrenchments have been employed in the defence from the earliest times. The Roman walls in Britain, the Great Wall of China, the earthworks in the Russian War of 1854-1855, in the American Civil War of 1861-1864, in the Russo-Turkish War of 1878, and the Russo-Japanese War of 1904-1905 are notable examples. But in no war previous to that of 1914-1918 have they played so important a part.