Knuckle under
Definition 1 of 1
Pro Tip 1/3Power Dynamics
Use 'knuckle under' to describe a situation where someone is overpowered or dominated. 
Despite his efforts, he had to knuckle under to the new manager's strict policies.
Pro Tip 2/3Informal Tone
'Knuckle under' is informal and better suited for casual conversation or storytelling. 
I hate to knuckle under, but I really need this favor from you.
Pro Tip 3/3Negative Connotation
The phrase often implies reluctance or a loss of struggle against an opposing force. 
The workers didn't want to, but they knuckled under to avoid losing their jobs.