fall back
phrasal verb with fall verb uk/fɔːl/ us/fɑːl/ fell | fallen
literary（常指因恐惧而）后退，后撤
to move back suddenly from someone or something, often because you are frightened
She fell back in horror/disgust. 她惊恐地／厌恶地往后退。
（军队）撤退
If an army falls back, it moves away from an enemy army in order to avoid fighting.
The infantry fell back in disarray. 步兵仓皇撤退。