The Monroe Doctrine was rapidly accepted as expressing the fundamental principle of American foreign policy. But under the influence of the powerful tradition which we have attempted to analyse, its significance was gradually changed; and instead of being interpreted as a proclamation that the great republic could not be indifferent to the fate of liberty, and would co-operate to defend it from attack in all cases where such co-operation was reasonably practicable, it came to be interpreted by average public opinion as meaning that America had no concern with the politics of the Old World, and that the states of the Old World must not be allowed to meddle in any of the affairs of either American continent. The world of civilisation was to be divided into water-tight compartments; as if it were not indissolubly one. Yet even in this rather narrow form, the Monroe doctrine has on the whole been productive of good; it has helped to save South America from becoming one of the fields of rivalry of the European powers. But it may be doubted whether the mere enunciation of the doctrine, even in this precise and definite form, has of itself been sufficient to secure this end. There is good reason to believe that the doctrine would not have been safe from challenge if it had not been safeguarded by the supremacy of the British Fleet. For throughout the last half-century all the world has known that any defiance of this doctrine, and any attack upon America, would bring Britain into the field. During all this period one of the factors of world-politics has been the existence of an informal and one-sided alliance between Britain and America. The alliance has been informal, because it has not rested upon any treaty or even upon any definite understanding. It has been one-sided, because while average opinion in America has been distrustful of Britain, has been apt to put unfavourable constructions upon British policy, and has generally failed to appreciate the value and significance of the work which Britain has done in the outer world, Britain, on the other hand, has always known that America stood for justice and freedom; and therefore, however difficult the relations between the two powers might occasionally become, Britain has steadfastly refused to consider the possibility of a breach with America, and with rare exceptions has steadily given her support to American policy. The action of the British squadron off the Philippines in 1898, in quietly interposing itself between the threatening German guns and the American Fleet, has, in fact, been broadly typical of the British attitude. This factor has not only helped to preserve the Monroe Doctrine from challenge, it has indirectly contributed to deepen the American conviction that it was possible, even in the changed conditions of the modern world, to maintain a complete isolation from the political controversies of the powers.