The campaign in German East Africa was much longer and harder than that in South West Africa. It had been begun under British command in November 1915. Smuts took command in February 1916 and stayed until the end of the following January, by which time the campaign was all but over. The circumstances of his appointment are recorded in 671–674.

A connected story of the campaign is not to be found in Smuts's papers. His own brief account of it appears in a preface to the best history of the campaign: General Smuts's Campaign in East Africa, by J. H. V. Crowe. But he wrote a number of letters from the front in which phases of the campaign are vividly described. The best of these letters were written to his wife. They are, in spite of the difficulties and hardships they recount, full of gusto and also of delight in the beauty of a country which fascinated him throughout his life. Other letters to his regular correspondents show what he was thinking about the larger issues of war and peace—the dangers of a ‘stalemate’, of a ‘war of attrition’, of ‘an inconclusive peace’ (681, 683, 685, 700). And letters to Wolstenholme, whose parcels of books reached Smuts at his headquarters, show that he was ‘still revolving my Holistic theory’ (702).