Robert Baden-Powell had become a national hero during the Boer War as a result of his successful defence of Mafeking, which was under siege from October 1899 to May 1900. The Mafeking Cadets, made up of local boys aged 12 to 15, acted as messengers throughout the siege, and had impressed him with their resourcefulness and courage. Baden-Powell had also published popular books on military scouting, including "Aids to Scouting for NCOs and Men", published in 1899. Though written for non-commissioned officers, the book became a best-seller and was used by teachers and youth organisations. In the years after the war Baden-Powell broached the idea of a new youth organisation with William Alexander Smith, founder of the Boys' Brigade, with whom he discussed setting up a Boys Brigade Scouting achievement. To test his ideas while writing "Scouting for Boys", Baden-Powell conceived of an experimental camp, creating a programme to take place on Brownsea Island during 1907. He invited his friend, Major Kenneth McLaren, to attend the camp as an assistant.