黑旗軍
The Battle of Paper Bridge was precipitated by a challenge by Liu Yongfu, who posted up placards in Hanoi on 10 May 1883 daring Rivière to come out and meet the Black Flag Army in the open field. Rivière believed that French prestige required him to respond to this challenge, and at dawn on 19 May led a column of around 450 French soldiers and sailors to attack the Black Flag Army in its positions at Phu Hoai, a few miles west of Hanoi. The column consisted of two companies of marine infantry, the landing companies of the French warships "Victorieuse" and "Villars", and three artillery pieces.