From that period down to the present moment, intervention in the internal affairs of other nations has been a prevailing practice, now cautiously and peaceably, now offensively and forcibly. Sometimes it was against the rights of men, sometimes it was in their favor. Sometimes England and France stood aloof, sometimes they took part. The Congress of Vienna, which undertook to settle the map of Europe, organized universal and perpetual intervention in the interest of monarchical institutions and existing dynasties. This compact was renewed at the Congress of Aix-la-Chapelle, in 1818, with the explanatory declaration, that the five great powers would never assume jurisdiction over questions concerning the rights and interests of another power, _except at its request_, and without inviting such power to take part in the conference,--a concession obviously adverse to any liberal movement. Meanwhile appeared the Holy Alliance, specially to watch and control the revolutionary tendencies of the age; but into this combination England most honorably declined to enter. The other powers were sufficiently active. Austria, Russia, and Prussia did not hesitate at the Congress of Laybach, in 1821, to institute armed intervention for the suppression of liberal principles in Naples; and again, two years later, at the Congress of Verona, these same powers, together with France, instituted another armed intervention to suppress liberal principles in Spain, which ultimately led to the invasion of that kingdom and the overthrow of its Constitution. France was the belligerent agent, and would not be turned aside, although the Duke of Wellington at Verona, and Mr. Canning at home, sought to arrest her armies by the mediation of Great Britain, which was directly sought by Spain and directly refused by France. The British Government, in admirable letters, composed with unsurpassed skill, and constituting a noble page of International Law, “disclaimed for itself, and denied for other powers, the right of requiring any changes in the internal institutions of independent states, _with the menace of hostile attack in case of refusal_”; and bravely declared to the imperial and royal interventionists, that, “so long as the struggles and disturbances of Spain should be confined within the circle of her own territory, they could not be admitted by the British Government to afford any plea of foreign interference”; and in still another note repeated that a “_menace of direct and imminent danger could alone, in exception to the general rule, justify foreign interference_.”[71] These were the words of Mr. Canning; but even Lord Castlereagh, in an earlier note, asserted the same limitation, which, at a later day, had the unqualified support of Lord Grey, and also of Lord Aberdeen. Justly interpreted, they leave no apology for armed intervention, except in case of direct and imminent danger, when a nation, like an individual, may be thrown upon the great right of self-defence.