At the outbreak of the war Breytenbach was Field Cornet of Ward 1, Bethal. He was promoted to Commandant of the Bethal Commando after Talana and saw extensive service during the Siege of Ladysmith. He then was part of the Boer withdrawal to the Eastern Transvaal, including the actions at Dalmanutha in August 1900.He lost an arm at Bakenlaagte (30 October 1901) but towards the end of the year he was back in the field.
However, on 5 January 1902 he and 10 of his men were surprised and captured by the 13th Hussars under Colonel Smithson. Captain Tremayne was subsequently promoted to Major "for singlehanded capture of Commandant Breytenbach".
Although Commandant Breytenbach was entitled to the DTD and Wound Riband, he applied for only an ABO medal in 1942, when he was 80 years old.
He died in 1948.