The British statesman Robert Stewart Viscount Castlereagh and 2d Marquess of Londonderry (1769-1822), as foreign secretary did much to consolidate a firm final international alliance against Napoleon and to establish the framework for a remarkably durable European peace settlement.

Robert Stewart was born in Ulster on June 18, 1769, son of Robert Stewart and Lady Sarah Seymour. His father, a substantial landowner and member of the Irish Parliament, was raised to the Irish peerage in 1789. As the eldest son, Robert held the courtesy title of Viscount Castlereagh from 1796 until he succeeded as Marquess of Londonderry in 1821. His schooling in Ireland was followed by a year at Cambridge and by a good deal of contact with the influential English families of his mother and stepmother, the Hertfords and the Camdens. In 1794 he married Lady Emily Hobart, daughter of the Earl of Buckinghamshire. Entering the Irish Parliament in 1790, he at first advocated...