In 1913, Macintosh served as president of the Cambridge University Athletics Club, won the Scottish title, and equaled the British record over 100 yards. He ran his last competition in 1914 and left to South Africa. After the start of World War I he was commissioned into the Argyll and Sutherland Highlanders. He died as a captain at age 26, from wounds sustained during the Second Battle of the Somme. He was buried in Senlis French National Cemetery.