Angered that his Chinese and Vietnamese allies had done little to support the Black Flag Army at Son Tay, Liu stood on the sidelines during the Bắc Ninh Campaign (March 1884).
Marah karena sekutu-sekutunya dari Tiongkok dan Vietnam tidak berbuat banyak untuk mendukung Pasukan Bendera Hitam di Son Tay, Liu berdiri di sela-sela selama Kampanye Bac Ninh (Maret 1884).