Castlereagh, Robert Stewart, 2d Viscount (kăˈsəlrā) [key], 1769–1822, British statesman, b. Ireland. Entering the Irish Parliament in 1790 and the British Parliament in 1794, he was acting chief secretary for Ireland at the time of the Irish rebellion of 1798. Having worked for the Act of Union of England and Ireland (1800), he resigned with William Pitt in 1801 when George III refused to allow Catholic Emancipation. President of the India board of control from 1802 to 1806, he also served (1805–6, 1807–9) as secretary of war. In the latter office, he planned the reorganization and expansion of the army and the effective coordination of British land and sea power. He dispatched a British expedition to Portugal, and after the early disasters in the Peninsular War he succeeded in putting Arthur Wellesley (later duke of Wellington) in command. The opposition of his colleague George Canning to Castlereagh's policies flared into a serious quarrel. Castlereagh accused Canning of political betrayal, and they fought (1809) a duel. Canning was wounded, and both resigned. As foreign secretary (1812–22), Castlereagh helped to organize the successful final coalition against Napoleon I, partly by secret treaties promising territorial changes. In the Treaty of Chaumont (1814) he obtained that "concert of Europe" later confirmed by the Quadruple Alliance. He advocated a moderate peace settlement for France, including restoration of the Bourbon monarchy and the limitation of France to her prewar boundaries. A dominant figure at the Congress of Vienna (1814–15; see Vienna, Congress of), Castlereagh worked for the establishment of the United Netherlands and the German Confederation. He favored an independent Poland but was compelled to accept a repartitioning of that country. Castlereagh placed great hope in the "congress system" agreed on at Vienna, by which the great powers would consult regularly for the maintenance of peace. However, he did not approve of outright intervention in the domestic affairs of other countries and protested, in increasingly explicit terms, the assumption of this right by the powers of the Holy Alliance. By the time of his death it is almost certain that he had decided to break with the wartime allies. In England, however, he was much criticized for his apparent cooperation with those same autocratic governments, and he was also blamed for repressive actions to curb unrest in England, though he was not directly responsible for them. He became (1821) the 2d marquess of Londonderry on his father's death. He committed suicide the next year. One of the foremost statesmen of his time, Castlereagh was cold in personality and lacked ability as an orator; he never gained an easy popularity and was hated by radicals like Shelley.
See biographies by C. J. Bartlett (1966) and J. Bew (2012); H. A. Kissinger, A World Restored (1957, repr. 1964).
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