Arthur James Balfour was British prime minister (1902-5) and foreign secretary (1916-19), a conservative and an intellectual. This is the first analysis of his thinking on a full range of international issues, such as British imperialism, Great Power relations in Europe, Africa, the Middle East, central Asia and the Far East, the First World War, the Russian revolution, Zionism, the League of Nations and, above all, the Anglo-American relationship. Balfour emerges with a distinctively conservative approach to foreign affairs that demonstrates a continuity of belief from his philosophical writings to his political practice.