The theory of the balance of power rested on several assumptions. It was held, more especially from the time of Grotius, in the early part of the 17th century, that the states of Europe formed one grand community or federal league, of which the fundamental principle and condition was the preservation of the balance of power; that by this balance (in the words of Vattel) was to be understood such a disposition of things, as that no one potentate or state shall be able absolutely to predominate and prescribe laws to the others; that all were equally interested in maintaining this common settlement, and that it was the interest, the right, and the duty of every power to interfere, even by force of arms, when any of the conditions of this settlement were infringed or assailed by any other member of the community. The principle can hardly be more tersely expressed than in the words of Polybius (lib. i. cap. 83): “Neque enim ejusmodi principia contemnere oportet, neque tanta cuiquam astruenda est potentia, ut cum eo postea de tuo quamvis manifesto jure disceptare ex aequo non queas.” Or, to borrow the language of Fénelon in his Instructions, drawn up by him for the guidance of the Duc de Bourgogne, “This attention to maintain a sort of equality and equipoise between neighbouring nations is the security of the general tranquillity. In this respect all neighbouring nations, trading with each other, form one great body and a sort of community. Thus, Christendom is a kind of universal republic, which has its interests, its fears, and its precautions to be taken. All the members of this great body owe it to one another for the common good, and owe it to themselves for the security of their country, to prevent the progress of any other members who should seek to overthrow this balance, which would turn to the certain ruin of all the other members of the same body. Whatever changes or affects this general system of Europe is too dangerous, and draws after it infinite mischiefs.” Whatever may be the value of these philanthropic principles, history reminds us that when they were most loudly professed they were most frequently violated, and that no cause of war seems to have been so frequent or so fatal as the spurious pretext of restoring peace and defending the general tranquillity of the world. Thus, it was to balance the power of the house of Austria that Cardinal Richelieu flung France into the quarrels of Germany in the Thirty Years’ War, and even lent her aid to the Protestant cause. It was to balance the encroaching and aggressive power of Louis XIV. that numerous combinations were formed between England, Austria, and Holland, which, after nearly half a century of almost uninterrupted contests and bloodshed, ended in the peace of Utrecht. The pretext of Frederick II., when he was meditating some act of rapine, generally was that he believed some hostile combination had been formed against him, which it was wise to anticipate. In short, no cause of war has been more frequently alleged and acted upon, than that a proper consideration for the balance of power rendered it necessary to take forcible measures to avert some remote or hypothetical danger.

It is obviously a maxim, not only of policy but of common sense and human nature, that the weak should combine to protect themselves against the strong, and that when the independence of minor states is threatened by the ambition or the overwhelming superiority of a power aiming at universal empire, they will do wisely to unite for the purposes of self-defence and resistance. Frederick II. himself says, in his Anti-Machiavel, where he laid down precepts which he did not practise, “When the excessive aggrandisement of one power threatens to overwhelm all others, it is the part of wisdom to oppose barriers to its encroachments, whilst there is yet time to stay the torrent. The clouds are seen to gather, the lightning announces a coming storm, and the sovereign who is unable to contend against the tempest will, if he is wise, unite himself with all those who are menaced by the same common danger. Had the kings of Egypt, Syria, and Macedonia confederated together against the Roman power, they would not have fallen under its oppressive yoke; an alliance prudently contracted, and a war carried on with energy, would have saved the ancient world from universal despotism.” So too, Hume, in his celebrated Essay on the Balance of Power, endeavours to show that the ancients were familiar with the principle both as statesmen and historians, and, for example, he avers that whoever will read Demosthenes’s oration for the Megalopolitans, will see the utmost refinements on this principle that ever entered into the head of a Venetian or European speculatist.

But with great respect to these illustrious authorities, they appear to have discussed, under the name of the balance of power, a principle which might more fitly be termed a theory of warlike alliances. The object of the balance of power, rightly understood, is not to carry on war with success, but to avoid war altogether, by establishing a common interest and obligation in the maintenance of the conditions of peace. When war is declared, public law is suspended, and each state must be guided by what it conceives to be its own interest and duty. If the theory of the balance of power has any value at all, it is not in the hour of violence and bloodshed, when the fate of nations may be decided on a field of battle, but rather in those negotiations which must eventually terminate the contest, which commonly bring together for that purpose the representatives of all the belligerents, and which are designed to provide against the recurrence of these calamities.

The ablest and most eloquent champion of the system of equipoise in the present century was the Chevalier von Gentz, who published his Fragments upon the Balance of Power in Europe in 1806, under the influence of the catastrophe which had subjugated the Continent, and who subsequently took an active part at the Congress of Vienna in the attempts to constitute a new system of European policy. Gentz defines the balance of power as “a constitution subsisting between neighbouring states more or less connected with one another, by virtue of which no one among them can injure the independence or essential rights of another, without meeting with effectual resistance on some side, and consequently exposing itself to danger.” And he rests this constitution on four propositions :—(1.) That no state must ever become so powerful as to coerce all the rest; (2.) That every state which infringes the conditions is liable to be coerced by the others; (3.) That the fear of coercion should keep all within the bounds of moderation; and (4.) That a state having attained a degree of power to defy the union should be treated as a common enemy. He argues that by a strict adherence to these principles wars would be averted, excessive power restrained, and the independent existence of the humblest members of the confederacy secured. But, for the reasons we have previously assigned, it is a fallacy to suppose that even the civilised states of Europe have ever naturally formed a confederacy, or that their relations are governed by common rules of action, recognised alike by all of them. That theory supplies a very insecure basis for the balance of power and the maintenance of peace. The law of nations, not being imposed or sanctioned by any supreme and sovereign authority, is, in fact, reducible to the general laws' of morality, which ought to regulate the dealings of mankind, except when it has been expressed and established in the form of a contract, binding on all the parties to that obligation. To determine the true character and limits of the balance of power, we must have recourse, not to vague general principles, but to positive law, framed in the shape of international contracts, which are termed treaties, and which have been sanctioned at different epochs of modern history by a congress of states. This historical treatment of the subject leads us to more tangible and solid ground; and it will be seen that on these occasions more especially attempts have been made to establish a balance of power in Europe upon the basis of general treaties; and that these attempts have been rewarded by considerable, though not by permanent, success in the 17th, 18th, and 19th centuries.

The first idea of a general congress, to put an end to the horrors of the Thirty Years’ War, and to adjust the conflicting claims of rival creeds and hostile princes, appears to have originated with the emperor of Germany in 1640. The attempt to restore peace by the authority of the Germanic Diet had failed. It became necessary to have recourse to mediating powers, and after a protracted preliminary negotiation, the Congress of Münster or Westphalia opened on the 11th July 1643,—the Catholic and Protestant belligerents being represented on the one hand, and the mediating powers, France, Sweden, Venice, and the Pope, on the other. We do not propose in this place to follow the train of these complicated negotiations. It is enough for our present purpose to remark that the great treaty which resulted from them, and was signed on the 24th October 1648, became the basis of the public law of Europe, and the first official recognition, of the existence of a European balance of power. The conditions established in Germany left the Catholic, the Lutheran, and the Reformed Churches in possession of their respective independence, whilst they relieved the minor princes from their strict dependence on the empire; but, above all. they conferred on France and Sweden, as mediating powers, the right of intervention for the purpose of upholding the provisions of the treaty. In other words, the balance which had been established between the states of Central Europe was regulated by external weights, which could be brought to bear upon it. The result of this combination, due mainly to Cardinal Mazarin, was certainly injurious to the unity and independence of Germany, and it tended to aid the aggressive and dictatorial power of Louis XIV. Nevertheless, the fundamental principles of the Treaty of Westphalia were recognised and renewed as the conditions of the general peace of Europe down to the French Revolution; they were not wholly absent from the minds of the negotiators at Vienna in 1815; and they only received their death-blow from the hand of the Prussian Government in 1866 and 1870. Whatever might be the merits of the Treaty of Westphalia, it had not that of securing to Europe an unbroken or durable peace; and even the territorial relations of France and Germany were altered within thirty years of that time by the conquest of Franche Comté and Alsace. But the wars of Louis XIV. were not general wars, until he engaged in the fatal attempt to place his grandson on the throne of Spain, and to unite the two crowns in the house of Bourbon. Efforts had been made, in view of the approaching extinction of the Spanish branch of the house of Austria, to preserve the balance of power by a timely partition of the vast dominions of the Spanish empire—a remarkable example of an attempt to prevent a formidable catastrophe by an equitable arrangement. But it may be doubted whether any arrangement in which so little account was taken of the wishes and traditions of nations could possibly have succeeded; and it unquestionably failed, because Louis XIV. did not hesitate to repudiate the treaties he had signed, and to avail himself of the last will and testament of Charles II., which had been extorted from the Spanish court by his intrigues. That event raised again the whole question of the balance of power in Europe. It was received as a doctrine of political faith that the union of the French and Spanish crowns in one family must be fatal to the independence of all other states; that it would replace the Stuarts upon the throne of England, and establish the ascendency of France and the Catholic party over Europe. It was therefore resisted by a coalition, of which England, Austria, and Holland were the principal members. France was at length reduced to the lowest point of humiliation, and in 1709 peace might have been obtained on every point but one. Louis refused to turn his arms against his own grandson, and the war continued till 1715. Philip V. retained the Spanish crown, and the relations of all the European states were once more adjusted with legal nicety at Utrecht. Great pains were taken to provide, by a system of renunciations, against the possibility of the union of the crowns of France and Spain on the same head, because it was held that such a contingency would be fatal to the balance of power in Europe. But these precautions did not prevent the conclusion, at a later period, of the family compact between the two branches of the house of Bourbon, which was regarded as a lasting danger to other countries, and was opposed by the whole strength of Britain and the genius of Chatham. The peace of Utrecht was denounced by Parliament and detested by the nation as an inglorious termination of a glorious war, and its authors were consigned to obloquy and exile; but it secured the peace of Europe for thirty years; it reduced the power of France; and had it not been for the German dominions of the house of Hanover, it might have been still longer before England was drawn into another war.

Hitherto the political system of Europe had comprised little more than the states of France, Austria, Spain, Sweden, and Holland, with the occasional intervention of Great Britain, more for the defence of the interests of others than of her own. But the 18th century witnessed a total change in the politics of the world. A new empire, Russia, arose in the north, under the genius of Peter and of Catherine; the ambition and military skill of Frederick II. raised Prussia from a secondary member of the German empire to a powerful and independent kingdom; the colonial empires of Spain, France, and Britain had extended their territorial interests to the continents of Asia and America, and to the eastern and the western isles, insomuch that wars, begun in Europe, soon raged on the banks of the Ganges and the St Lawrence; and the declaration of independence of the United States of America called into beiDg a new and powerful people of the future. The partition of Poland, which was commenced in 1772, marked a new era of aggressive revolutionary policy; it was a gross invasion of the principle of the balance of power, effected by three powers, jealous of their respective strength, but indifferent to the rights of an independent nation and to the opinion of Europe. That lawless act was the prelude to more violent attacks on the sovereignty and nationality of many countries, for before the century closed the French Revolution, and the wars that followed it, crushed to atoms the ancient fabric of Europe. Whilst events of this magnitude were occurring in the world, it is obvious that the theory of the balance of power was entirely displaced and dislocated. New elements were at work over a far wider area; new sources of power and influence were opened of far more importance than those territorial and dynastic questions which occupied the statesmen of Münster and of Utrecht; ancient land-marks were swept away; minor states were annihilated; and the temporary domination of Napoleon over a great portion of the continent of Europe seemed to have overthrown the balance of power for ever. In those dark and evil days pubhc writers like Gentz and Mackintosh still maintained the principle that peace could only be restored by a due recognition of the rights and independence of every nation, and England adhered inflexibly to the policy of combining the scattered elements of Europe against the common enemy. Half a dozen times over these coalitions failed; but they succeeded at last, and this country had the glory of playing no inconsiderable part in the restoration of the liberties of all other nations against foreign aggression. Great as were the cost and the burden of that tremendous war, we still hold that the prodigious power of France and the boundless ambition of Napoleon left us no honourable alternative but to pursue it; and, as Mr Fox himself discovered when he conducted the negotiations of 1806, it was impossible to conclude peace with France without basely surrendering the whole interests of Europe to universal oppression, and without exposing this country to be at last the victim of a power which had devoured all the rest. The principle of the balance of power, in the sense of mutual defence, was never asserted with greater energy than it was by this country in that struggle, and we do not regret it. “As long,” says Bacon, “as men are men, and as long as reason is reason, a just fear will be a just cause of a preventive war; but especially if it be part of the case that there be a nation that is manifestly detected to aspire to new acquests, then other stateβ assuredly cannot be justly accused for not paying for the first blow, or for not adopting Polyphemus’s courtesy, to be the last that shall be eaten up. ”— {Speech concerning a }f r ar with Spain.}

Upon the fall of Napoleon in 1814 it became the common interest, and the universal desire, of all the sovereigns and nations of Europe to restore peace upon a settled basis, to re-establish the authority of public law, to reinstate the rightful owners in the possessions and dominions they had been forcibly deprived...