The interventions of Britain in continental politics were generally on behalf of the principles of nationality and self-government. Under the influence of Castlereagh and Canning the British government gradually broke away from the Holy Alliance formed to suppress all protests against the settlement reached after Napoleon's fall; and Britain interposed with decisive effect at the battle of Navarino in 1827, which secured the independence of Greece from Turkey. More diplomatic intervention assisted the South American colonies to assert their independence of the Spanish mother-country; and British volunteers helped the Liberal cause in Spain and Portugal against reactionary monarchs. Belgium was countenanced in its successful revolution against the House of Orange, and Italian states in their revolts against native and foreign despots; the expulsion of the Hapsburgs and Bourbons from Italy, and its unification on a nationalist basis, owed something to British diplomacy, which supported Cavour, and to British volunteers who fought for Garibaldi. The attitude of Britain towards the Balkan nationalities, which were endeavouring to throw off the Turkish yoke, was more dubious; while Gladstone denounced Turkish atrocities, Disraeli strengthened Turkey's hands. Yet England would have been as enthusiastic for a liberated and united Balkan power as it had been for a united Italy but for the claims of a rival liberator, Russia. Russia was the bugbear of two generations of Englishmen; and classical scholars, who interpreted modern politics by the light of ancient Greece, saw in the absorption of Athens by Macedon a convincing demonstration of the fate which the modern barbarian of the north was to inflict upon the British heirs of Hellas. India was the real source of this nervousness. British dominion, after further wars with the Mahrattas, the Sikhs, and the Gurkhas, had extended up to the frontiers of Afghanistan; but there was always the fear lest another sword should take away dominion won by the British, and in British eyes it was an offence that any other power should expand in Asia. The Russian and British spheres of influence advanced till they met in Kabul; and for fifty years the two powers contested, by more or less diplomatic methods, the control of the Amir of Afghanistan. Turkey flanked the overland route to India; and hence the protection of Turkey against Russia became a cardinal point in British foreign policy. On behalf of Turkey's integrity Great Britain fought, in alliance with France and Sardinia, the futile Crimean War of 1854-1856, and nearly went to war in 1877.