High Quality Content by WIKIPEDIA articles! The Battle of Phu Hoai (15 August 1883) was an indecisive engagement between the Tonkin Expeditionary Corps and Liu Yongfu`s Black Flag Army during the early months of the Tonkin campaign (1883–1886). The battle took place during the period of increasing tension between France and China that eventually culminated in the Sino-French War (August 1884–April 1885).