On 5 May, Campbell arrived at Nairobi and was attached to the King's African Rifles, serving in a camp two miles outside the city. After having worked as a military censor, he was transferred in June to the 12th Observation Unit of the commando force being trained for jungle warfare against the Imperial Japanese Army. However, any hope of combat was thwarted when Campbell in late July suffered a new injury to his damaged hip in a fall from a motorcycle. He was sent to hospital in Nairobi, where the doctors examined an X-ray of his hips and declared him unfit for active service.