định was born in the bình sơn district in the quảng ngãi prefecture in quảng nam province in central vietnam. the son of a military mandarin named trương cầm, định went south in the 1830s when his father was posted to gia định as the provincial commander. định enjoyed a reputation among the locals for his martial skills and knowledge of the military classics. he married the daughter of a wealthy resident of tân an in nearby dinh tuong province, having moved there after his father's unexpected death. it was likely that he would have returned to central vietnam if he had not married.