From Longman Dictionary of Contemporary Englishsoften somebody/something ↔ up phrasal verb1 informalPERSUADE to be nice to someone before you ask them to do something, so that they will agree to help you She was just softening me up.2 PMto make an enemy weaker so that they are easier to attack Use artillery to soften up the enemy forces.3 to make something less hard or rough → soften→ See Verb table
Examples from the Corpus
soften up• I can see what they mean about women softening you up.• Iced sardines are trodden underfoot to soften them up.• It didn't really matter though, because the mulberries softened it up.• Here, bacteria get to work on it, softening it up and making it ready for chewing.• You want to soften me up, don't you?• Psycho-shock, I told myself, a way to soften you up for interrogation.• He was beginning to wonder if they weren't already softening him up for some kind of a change.• To soften me up for the kill? 