They have been particularly led to do this since the introduction of firearms, because firearms give the individual man a wider area over which he can stop his enemy. But in every form of war, primitive or modern, these great lines have existed. The Wall of China is one great instance of them; the Roman Wall over the North of Britain, from sea to sea, is another; and the long-fortified Roman frontier from the Rhine to the Danube was a third. The generals of Louis XIV, in a line called by the now famous name of La Bassée, established on a smaller scale the same sort of thing for a particular campaign. There are hundreds of examples. But the characteristic novelty of the present war, and the point in which it differs from all these ancient examples, is the _rapidity_ with which such lines are established by the great numbers now facing each other, armed as they are by weapons of very long range. [Illustration: This gives you at a glance an idea of the numbers engaged and the time occupied in some famous battles of the past. Each little figure in the above drawings represents 5000 men. It will be seen that even the Battle of Mukden is scarcely comparable in duration with the months-long contests of the present war.] Forty-eight hours’ preparation, or even less, is enough for troops to “dig themselves in” over a stretch of country which, in the maximum case of the French lines, is 300 miles in extent. Every slight advance is guaranteed by a new construction of trenches, every retirement hopes to check the enemy at another line of trenches established at the rear of the first. Roughly speaking, half a million of men could hold one hundred miles of such a line under modern conditions, and, therefore, when the vast numbers which such a campaign as this produces are brought into the field, you can establish a line stretching across a whole continent and incapable of being turned. That is what has been done in France during the present war. You have got trenches which, so long as they are sufficiently held in proportion to the numbers of the offensive, are impregnable, and which run from the Swiss Mountains to the North Sea. It is possible that you may have to-morrow similar lines running from the Carpathians to the Baltic. Though this I doubt, first, because in the Eastern theatre of war Russia can produce perpetually increasing numbers to assault those lines; secondly, because the heavy artillery essential for their support cannot be present in large numbers in the East. One may sum up, therefore, upon this particular novel feature of the present campaign and say that it is mainly due to the very large numbers engaged, coupled with the retaining power of the heavy artillery which the Germans have prepared in such high numerical superiority over their opponents. It is not a feature which you will necessarily find reproduced by any means in all the wars, even of the near future, or in the later stages of this war.