Alexander, Peter and William were the sons of Donald and Jean Campbell of Inverell Station. They all worked on family properties.
William was the first of the brothers to enlist. He had been 18 months in the local 5th Light Horse unit when at the age of twenty six he enlisted at Inverell. He was one of thirty one men farewelled at Inverell Town Hall in September 1915 and presented with the Inverell medal and two pairs of socks. He joined the 7th Light Horse Regiment, 14th Reinforcement and left Australia for Egypt on HMAT A57 Malakuta in March 1916. Like many other men, he became ill with malaria in 1918. William returned to Australia in January 1919. His name is inscribed on the Inverell Honor Roll.
Alexander enlisted at Inverell in December 1916 when he was forty three years old, having previously been rejected due to his feet. He joined the 6th Light Horse, 24th Regiment and left Australia for Egypt on HMAT A42 Boorara in May 1917. He was eventually promoted to Temporary Squadron Quartermaster. Alexander returned home in July 1919.
Peter was thirty two when he enlisted at Inverell in May 1917. He became a Gunner with the Field Artillery Brigade, Reinforcement 30 and left Australia on HMAT A15 Port Sydney in November. After spending three months in Egypt he was sent to France in April 1918. Peter was wounded in action in October and invalided to England for hospital treatment for a gunshot wound to his left arm. Peter returned home and was medically discharged in March 1919.