the son of john fawcus, he was born at south charlton in northumberland. he was educated at durham college, before studying medicine at the durham university college of medicine. during this time he played rugby union for durham and northumberland, as well as debuting in minor counties cricket for northumberland in the 1898 minor counties championship. after completing his studies at durham, fawcus was commissioned into the british army as a lieutenant with the royal army medical corps in may 1900. he served in the second boer war, taking part in operations in natal, cape colony, orange free state and transvaal colony. he was awarded both the queen's south africa medal and the king's south africa medal. he was promoted to the rank of captain in may 1903, and obtained a diploma in public health in 1905. at his examination for promotion to major in 1907 he obtained a first-class certificate enabling him to year's acceleration of promotion, something only two other officers in the british army had achieved to that point.