soften up

phrasal verb

softened up; softening up; softens up

1

: to treat (someone) very well or kindly in order to make that person more likely to help one, give one something, etc.

He tried to soften her up by buying her flowers.

2

: to weaken (an enemy) through military attacks

They used artillery to soften up the enemy's defenses before launching a full-scale attack.