Palmerston, Henry John Temple, 3d Viscount, 1784–1865, British statesman. His viscountcy, to which he succeeded in 1802, was in the Irish peerage and therefore did not prevent him from entering the House of Commons in 1807. Initially a Tory, he served (1809–28) as secretary of war, but he differed with his party over his advocacy of parliamentary reform and joined (1830) the Whig government of the 2d Earl Grey as foreign minister. A firm believer in liberal constitutionalism, Palmerston was instrumental in securing the independence of Belgium (1830–31), and in 1834 he formed a quadruple alliance with France, Spain, and Portugal to help the Iberian countries put down rebellions aimed at restoring absolutist rule. He also organized the joint intervention with Russia, Austria, Prussia, and a reluctant France to prevent the disintegration of the Ottoman Empire as a result of the revolt of Muhammad Ali of Egypt (1839–41). He was in opposition during Sir Robert Peel's administration (1841–46) but returned to the foreign office under Lord John Russell. Palmerston was an impulsive man who often acted without consultation; during his second period as foreign secretary he succeeded in offending not only foreign powers but also his colleagues and Queen Victoria. He quarreled with France in the affair of the Spanish Marriages (1846; see Isabella II), gave encouragement to the European revolutionaries of 1848, and in 1850 caused widespread outrage by blockading Greece in order to secure compensation for Don Pacifico, a Portuguese merchant claiming British citizenship, whose house in Athens had been destroyed in a riot. Finally his unofficial and unauthorized approval of the coup in France by Napoleon III led to his dismissal in 1851. Nevertheless he became home secretary in 1852 and in 1855 succeeded the 4th earl of Aberdeen as prime minister. His vigorous prosecution of the Crimean War increased his already great popularity, as did the effective suppression of the Indian Mutiny, and although he lost office in 1858, he returned to power in 1859 and remained prime minister until his death. His attitude greatly facilitated the progress of the Italian Risorgimento and the proclamation (1861) of the kingdom of Italy, but his attempt (1864) to help the Danes in the Schleswig-Holstein question was unsuccessful. He maintained British neutrality in the American Civil War, despite his sympathy for the South and despite the irritating Trent Affair. Palmerston was not much interested in internal affairs, but he did firmly oppose further parliamentary reform. His diplomacy, reckless and domineering though it frequently was, usually served to advance British prestige.
See biographies by H. Lytton Bulwer and E. Ashley (5 vol., 1870–76), D. Southgate (1966), J. G. Ridley (1970), K. Bourne (Vol. 1, 1982); study by C. K. Webster (2 vol., 1951; repr. 1969).