Britain was gratified by the way in which this former anti-imperial fighter transmuted into a loyal exponent of the Commonwealth and a willing supporter of the wartime government. Winston Churchill, who had been captured in South Africa while working as a journalist during the Boer War, was a lifelong admirer of Smuts, and relied heavily on his counsel during World War II. In 1917, Churchill welcomed Smuts to London in the most fulsome terms: “At this moment there arrives in England from the outer marches of the Empire a new and altogether extraordinary man.” But Smuts’s forays into international politics came at a cost. He was increasingly vilified at home by Afrikaner nationalists as the “handyman of the empire” — a term originally used as praise by British newspapers.

Along with his vital contribution to defining the Commonwealth, Smuts played an important part in conceiving of the League of Nations itself. Concerned about how to achieve long-term peace in Europe, and watchful about the threat of Bolshevism, he argued that the terms imposed on Germany by the Treaty of Versailles were overly harsh: The same spirit of magnanimity — or “appeasement,” in Smuts’s words — that had achieved a workable peace between Britons and Boers ought now to be demonstrated in the case of German reparations. Smuts encouraged John Maynard Keynes to write his seminal critique of the treaty, “The Economic Consequences of the Peace,” and in 1918 wrote a proposal of his own: “The League of Nations: A Practical Suggestion.”

The ideas contained in this pamphlet envisioned the League as a means to fill the vacuum left by Europe’s broken empires. Smuts saw the Commonwealth as an “embryo league of nations because it is based on the true principles of national freedom and political decentralization.” In spare prose, Smuts topped his talents as a lawyer with a sprinkling of inspirational idealism, translating President Woodrow Wilson’s aspirational Fourteen Points into a workable instrument for a peace “founded in human ideals, in principles of freedom and equality, and in institutions which will for the future guarantee those principles against wanton assault.”

Lloyd George commended Smuts’s ideas. Wilson was enthused as well: He invited Smuts to his residence at the Hôtel Crillon in Paris in January 1919, and incorporated some of Smuts’s ideas in his own proposals for the League. Smuts and Botha were unable to persuade the Peace Conference to allow Germany’s former colonies in the Pacific and Africa — which Smuts caricatured as “inhabited by barbarians, who not only cannot possibly govern themselves” — to pass directly to New Zealand and South Africa. Still, the Boer generals got the next best thing: Under the League’s mandate system, in which it acted as the trustee for less “civilized” nations deemed not ready for independence (and which Smuts helped design), South Africa effectively took over South West Africa, governing until it finally gained its independence as Namibia in 1990.

Smuts’s approach to politics was shaped by, of all people, Walt Whitman. While studying for a law degree at Cambridge, he wrote a treatise, “Walt Whitman: A Study in the Evolution of Personality,” in which he argued that the American poet exemplified an expansive conception of freedom rooted in pantheism and human potential, rather than religiosity. Smuts went on to develop this approach as “holism,” which he outlined in another treatise : Evolution pushed humans and societies to join ever larger wholes, from small local units to nations and commonwealths, culminating in global forms of association like the League.

Smuts’s approach to politics was shaped by, of all people, Walt Whitman.