defence on certain points, in fact, to create fortresses, greater or less in proportion to his fear of the enemy and his intelligent appreciation of the degree of sacrifice it was worth while to make to obtain security. A barbarian horde could be stopped by any barrier which could not be set on fire or escaladed without ladders or appliances. Ruses, such as the wooden horse of Troy, then became the fashion, and these had to be met by the cultivation of a higher order of intelligence, which naturally throve best in a crowded community, where each felt his dependence on his neighbour. Thus, for ages, the fort or fortress limited barbarian encroachments, and made possible the growth of civilization in the plains. Ultimately, when the civilized communities grew into contact with one another, developed antagonistic interests, and fell out with one another, intelligence was brought to bear on both sides, and the assailant met fortifi- cation with siege-craft. Then the whole cycle worked itself out again. To carry out a siege, men in numbers had to be concen- trated and fed whilst concentrated. The stores for attack were also heavy and difficult to convey, hence roads developed in- creased importance, and troops had to be abstracted from the fighting force to protect them. Thus again a limit of striking radius was fixed for the invader, and in proportion as the dimensions of the invaded country exceededÂ«this radius, and its people made the requisite sacrifices to maintain their fortifica- tions in order, the continued existence and growth of the smaller country was assured. Broadly, this equilibrium of forces remained for generations; the smallest states were eaten up, the larger ones continued to exist side by side with far more powerful enemies, but only on condition of their readiness to make the requisite sacrifice of their personal liberty and the property of their constituent units.
Then came the introduction of gunpowder and of siege artillery, and a fresh readaptation of conditions, which culmin- ated in the Netherlands during the 17th century and forms the starting-point of all modern practice.
Essentially the change consisted in this, viz. that in spite of the superiority of the cannon-ball to the battering-ram, yet to attack a wall effectively many guns had to be employed, and while the duration of the siege was enormously shortened, a far greater strain was thrown on the line of supply, for not only did guns weigh as much as their predecessors but they could expend their own weight of ammunition in a day. Hence the impor- tance of good roads became enhanced and correspondingly the incentive to attack the fortresses which guarded them. In com- parison to the money devoted to modern armies, the sums sunk on passive defences during the 16th and 17th centuries were colossal, but they could not keep pace with the progress of the attack, and once more fresh readjustment of means to end became necessary. The obvious course was to carry the war into the enemy's country from the outset, but since this transferred the burden of the siege upon the aggressor, the latter was compelled to develop the standing mercenary army, as feudal levies could not keep the field long enough to reduce a fortress. Mercenary armies, however, were difficult to keep together. They had to be tactfully commanded to ensure contentment, and allowed to main- tain social order amongst themselves, and the prospect of loot while on active service had to be held out to them. The sack of a city became thus the absolute and undeniable right of the soldiers. If in this or any other way their employer broke his contract, individuals promptly deserted to the other side. But this right of sack led to a recrudescence of the spirit of resistance in the fortresses (War of Dutch Independence and Thirty Years' War), and hence to a reaction in favour of greater humanity in warfare. But this was only obtained by the concession of a higher scale of pay and comfort to the men, which again threw an increased strain upon the communications, and also upon the treasure chest of their employer.
The growth of the mercenary system, and the facility with which such men could and did change their allegiance, led very rapidly to almost complete uniformity in the composition, training and tactical methods of all armies. Every one knew in advance the degree of effort his adversary proposed to put
forward in the next campaign, and made corresponding prepara- tions to meet him. Practically the king desiring to make wai submitted his idea to the best-known generals of his day and asked them to tender for its execution. The king, on his side, generally agreed to find the bulk of the labour â€” his standing army, re- inforced by auxiliaries to any desired extent â€” and as in the case of a modern government contract, the lowest tender was almost invariably accepted, with a pious exhortation to the successful competitor to spare his employer's troops to the best of his ability. Thus the opposing generals took the field, each equally fettered by the conditions of his tender. But two such armies, alike in almost every respect, were far too closely matched to be able easily to gain a decision in the open field. Once they were committed to a battle it was impossible to separate them until sheer physical exhaustion put a stop to the slaughter, and these highly trained men were difficult and expensive to replace. Naturally, then, the generals sought to destroy the existing equilibrium by other means. Primarily they took to strong entrenchments, but the building of these being a matter of time, the communications grew in importance and attempts agadnst them became more serious. One side or the other, consequently, to cover its communications, so extended its front that at length lines stretched right across whole frontiers till their flanks rested on the sea, or on some great fortress or neutral territory. The two armies would then face one another for months, each exhausting every device to induce the other to concentrate on one part of his front whilst an attempt was made by a rapid move to carry a relatively unguarded point elsewhere, e.g. Marlborough's surprise of the Ne plus ultra lines (see Spanish Succession). During such periods of immobility the works grew to the solidity of permanent fortifications, with wide and deep ditches, and with every obstacle known' to engineers, whilst to render them defensible by the minimum number of muskets, they were laid out so as to cross their fire over and over again opposite every weak point in their tracing. No amount of battering could alter their general trace, and so they remained defensible as long as their garrisons could be trusted to line the parapets at all. This state of things must have continued until progress in artillery had evolved a weapon with sufficient accuracy and shell power to drive the defenders from their parapets and keep them away till the last moment preceding assault, had not fresh factors evolved themselves from causes at work under totally different topo- graphical limitations and conditions.
First amongst these comes the accession to the throne of Prussia of a king who was commander-in-chief of his own army, and as such responsible to no one for the use he chose to make of it. This would really remove him at once from the category of strategists in the restricted sense in which the term is now employed, but since no convenient word exists to define the action of a ruler playing the double part of soldier and governor, it is convenient both in his case and in that of Napoleon to use the expression to cover the wider sphere. The permanence of the association between king and army enabled Frederick the Great to train his men specifically for the work he intended them to perform. Realizing to the full the value of the foundation laid by his father in developing to its utmost the fire power of the infantry, he devoted special attention to imparting to them a skill and rapidity in manoeuvre which ensured that in the open field his generals would always be able to place the muskets at their disposal in the best positions relatively to the enemy; and his cavalry were trained to such a pitch of mobility and precision in drill that they could be relied on to arrive at the appointed time and place to reap the fruits which the infantry fire had sown. To these startling innovations the Austrians had no new ideas to oppose. The old school, the survival of the fittest in the special theatre df its growth, i.e. the Netherlands and the Rhine, could not deal with the complete change in topographic surroundings â€” the far wider area of operations, the comparative scarcity of fortresses and the general practicability of the country for the movement of troops â€” not trains â€” off the roads. Frederick, relying absolutely on the intrinsic superiority of his army, knew that if he could catch his enemy in the open victory