The story of Hussein Onyango Obama’s political activism will make Kenyans proud, and might also give some Americans a new insight into their President-elect. Having answered the call to join the British Army during the Second World War, Barack Obama’s grandfather was among 75,000 Kenyans who served in Burma. Demobilised after the war, they came home with bulging pockets and high expectations. But having fought for freedom against the Japanese, they returned to a colony that had little to offer.

Unable to find dignified jobs, and thwarted in their efforts to invest their savings in small businesses by colonial rules and regulations, the ex-soldiers became disillusioned and dangerous. Obama plied his trade as a cook, and took domestic service with a British Army officer in the White Highlands.

As a new nationalist politics emerged after 1945 to challenge colonial rule in Kenya, the returning soldiers were in the vanguard of protest. Some affiliated to the KCA (Kikuyu Central Association). Later many more flocked to the broader-based KAU (Kenya African Union) that replaced the KCA in 1946. Obama, a Luo from Nyanza province in the west of the country, was among many for whom the nationalist reach of the KAU held appeal.

The KAU had begun organising the collection of funds by 1947. The next year a more radical group within the KAU, led by former army comrades from the Burma front, had secretly begun other collections that would buy the weapons with which the Mau Mau embarked upon its rebellion.

Was Obama connected with this radical ginger group? It is impossible for us to know for sure, and it is doubtful that even his family would have been aware of the political machinations within the KAU at the time, but it does seem the most plausible reason for his arrest and trial in 1949.

Those convicted of political subversion, or of membership of unregistered or banned political organisations, were liable to prison sentences. Violence was endemic in Kenya’s penal system long before the Mau Mau rebellion. Even in the 1930s and 1940s beatings and other punishments were routine. As a prisoner convicted of a political charge, Obama would certainly have been subjected to interrogations by Special Branch, who by 1950 were keen to find out as much as they could about the embryonic Mau Mau movement.

His disillusionment with the British after his incarceration is hardly surprising. But it seems not to have dented his political will. His son, Barack Obama’s father, briefly returned to Kenya after his education in the US and became a supporter of Kenya’s ruling nationalist party under Jomo Kenyatta. But when, in 1965, Kenyatta reneged on his promises to bring social democracy to Kenyans through building a welfare state and consolidating land reform, Obama’s father took up his pen. Writing in the influential magazine the East African Journal, he chastised Kenyatta and his Government for lacking the courage of their convictions. He lamented that without the reforms that were so urgently needed, Kenya’s social problems would haunt its future.

Amid the burning farms and violent mayhem of the early months of 2008, these words were grimly prophetic.

David Anderson is Professor of African Politics and director of the African Studies Centre at the University of Oxford

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