1.
If you ~, you move backwards a short distance away from someone or something.
He fell back in embarrassment when he saw that Ross had no hair at all...
The congregation fell back from them slightly as they entered.
PHRASAL VERB: V P, V P from n
2.
If an army falls back during a battle or war, it withdraws.
The Prussian garrison at Charleroi was falling back.
PHRASAL VERB: V P