At the age of 13 Keegan contracted orthopaedic tuberculosis, which subsequently affected his gait. The long-term effects of this rendered him unfit for military service, and the timing of his birth made him too young for service in the Second World War, facts he mentioned in his works as an ironic observation on his profession and interests. The illness also interrupted his education in his teenage years, although it included a period at King's College, Taunton and two years at Wimbledon College, which led to entry to Balliol College, Oxford in 1953, where he read history with an emphasis on war theory. After graduation he worked at the American Embassy in London for three years.